Equipment Financing: Complete Guide to Funding Business Equipment

What Is Equipment Financing and How Does It Work?

Quick Answer: Equipment financing is a loan or lease specifically designed to purchase business equipment, where the equipment itself serves as collateral. You apply through banks, equipment dealers, or online lenders, receive approval in 1-5 days, and make monthly payments over 2-7 years. The lender holds a lien on the equipment until you pay off the loan, at which point you own it outright.

Equipment financing allows businesses to acquire necessary machinery, vehicles, technology, and other equipment without paying the full purchase price upfront. Instead of depleting cash reserves or credit lines, businesses spread the cost over time through monthly payments that match the equipment's useful life and revenue-generating potential.

The financing structure is straightforward. You identify the equipment you need, obtain quotes from suppliers, and apply for financing through a lender. The lender evaluates your creditworthiness and the equipment's value, then approves a loan or lease for 80-100% of the purchase price. You make a down payment (typically 10-20%), and the lender pays the supplier directly. You take possession of the equipment immediately and begin making monthly payments.

The equipment serves as collateral, meaning the lender can repossess it if you default on payments. This collateral reduces the lender's risk, making equipment financing easier to obtain and less expensive than unsecured business loans. According to the U.S. Small Business Administration, equipment financing is one of the most accessible forms of business credit because the collateral provides security for lenders.

Interest rates vary based on your credit score, time in business, equipment type, and whether the equipment is new or used. New equipment typically qualifies for rates of 6-15%, while used equipment may carry rates of 10-30%. Terms range from 2 years for technology that depreciates quickly to 7 years for heavy machinery with long useful lives.

Types of Equipment Financing

Quick Answer: The three main types are equipment loans (you own the equipment, make fixed monthly payments, and keep it after payoff), equipment leases (you rent the equipment with an option to buy at lease end), and equipment lines of credit (revolving credit for multiple equipment purchases). Loans are best for long-term assets, leases for equipment that needs frequent upgrades, and lines of credit for businesses with ongoing equipment needs.

Equipment Loans

Equipment loans are traditional term loans secured by the equipment being purchased. You borrow a specific amount, receive the funds to purchase the equipment, and repay the loan with interest over a fixed term. At the end of the loan term, you own the equipment outright with no further obligations.

Loan amounts typically range from $5,000 to $5 million, with most lenders financing 80-100% of the equipment's value. Down payments of 10-20% are standard, though some lenders offer 100% financing for borrowers with excellent credit. Interest rates range from 6% to 30% depending on creditworthiness and equipment type.

Terms are structured to match the equipment's useful life. Technology equipment like computers and software typically has 2-3 year terms, vehicles and light machinery have 3-5 year terms, and heavy equipment like construction machinery or manufacturing equipment can extend to 7 years. Matching the loan term to the equipment's useful life ensures you're not making payments on obsolete or worn-out equipment.

Equipment loans offer several advantages. You own the equipment from day one, allowing you to modify or sell it as needed. Monthly payments are predictable and fixed, making budgeting easier. Interest and depreciation are tax-deductible, and you may qualify for Section 179 deductions allowing immediate expensing of up to $1.16 million in equipment purchases. Forbes reports that equipment loans are ideal for businesses planning to use equipment for its entire useful life.

Equipment Leases

Equipment leases allow you to use equipment without purchasing it outright. You make monthly lease payments for a specified term, and at lease end, you can purchase the equipment for its residual value, return it, or lease newer equipment. Leases are particularly popular for equipment that requires frequent upgrades or has high obsolescence risk.

Two main types of equipment leases exist: capital leases (also called finance leases) and operating leases. Capital leases function similarly to loans, with ownership transferring to you at lease end for a nominal fee. You record the equipment as an asset on your balance sheet and can claim depreciation deductions. Operating leases are true rentals where you return the equipment at lease end. Lease payments are fully tax-deductible as operating expenses, but you don't own the equipment or claim depreciation.

Lease terms typically range from 2 to 5 years, with monthly payments lower than equivalent loan payments because you're only paying for the equipment's depreciation during the lease term, not its full value. At lease end, you can purchase the equipment for its residual value (typically 10-25% of original cost), extend the lease, upgrade to newer equipment, or return it.

Leasing offers several benefits. Lower monthly payments preserve cash flow, making it easier to afford newer or more expensive equipment. You can upgrade to the latest technology at lease end without selling used equipment. Lease payments are typically 100% tax-deductible as operating expenses. However, you don't own the equipment, and total costs over multiple lease cycles can exceed purchase costs. NerdWallet notes that leasing works best for equipment that needs frequent upgrades, such as computers, medical devices, and technology systems.

Equipment Lines of Credit

Equipment lines of credit provide revolving access to capital specifically for equipment purchases. Similar to a business credit card, you're approved for a maximum credit limit and can draw funds as needed to purchase equipment. You only pay interest on the amount borrowed, and as you repay the balance, credit becomes available again for future purchases.

Credit limits typically range from $10,000 to $500,000, with interest rates of 8-25% depending on creditworthiness. Lines of credit are ideal for businesses with ongoing equipment needs, such as contractors who regularly purchase tools and machinery, or restaurants that frequently upgrade kitchen equipment.

The flexibility of equipment lines of credit makes them attractive for growing businesses. You can purchase multiple pieces of equipment over time without reapplying for financing. Draw periods typically last 2-3 years, during which you can borrow and repay repeatedly. After the draw period ends, the line converts to a term loan with fixed monthly payments over 2-5 years.

Equipment lines of credit work best when you need flexibility to purchase equipment opportunistically, such as when suppliers offer discounts or when business growth requires quick equipment acquisition. However, variable interest rates mean monthly payments can fluctuate, and credit limits may be lower than single equipment loan amounts.

Equipment Financing Qualification Requirements

Quick Answer: To qualify for equipment financing, you typically need 2+ years in business (1+ for strong applicants), personal credit score of 600+ (680+ for best rates), positive cash flow to cover equipment payments, and 10-20% down payment. Startups can qualify with strong personal credit, substantial down payments (20-30%), and equipment that holds value well. Approval is easier than working capital loans because equipment serves as collateral.

Credit Score Requirements

Equipment financing is more accessible than many other business loans because the equipment serves as collateral, reducing lender risk. Most lenders accept credit scores as low as 600, though rates improve significantly with higher scores. Borrowers with scores of 680+ qualify for the best rates (6-15%), while scores of 600-679 face rates of 15-25%, and scores below 600 may see rates of 25-30% or require alternative lenders.

Lenders evaluate both personal and business credit scores. For newer businesses without established business credit, personal credit carries more weight. As your business matures and builds credit history, business credit scores become increasingly important. Maintaining clean credit with no recent bankruptcies, foreclosures, or major delinquencies significantly improves approval odds.

Time in Business and Revenue Requirements

Most traditional lenders prefer businesses with at least 2 years of operating history, demonstrating stability and the ability to generate consistent revenue. However, many lenders will consider businesses with 1 year of operations if they show strong revenue growth and profitability.

Startups and newer businesses can still qualify for equipment financing, particularly if they have strong personal credit (720+), substantial down payments (20-30%), and are purchasing equipment with high resale value. Some lenders specialize in startup equipment financing and focus more on the equipment's value and the owner's experience than operating history.

Revenue requirements vary by loan amount and equipment type. As a general rule, lenders want to see monthly revenue of at least 3-4 times the monthly equipment payment. For example, if the equipment payment is $2,000 per month, lenders typically want to see monthly revenue of $6,000-$8,000 or more. This ensures you have sufficient cash flow to cover the payment while maintaining operations.

Down Payment and Loan-to-Value Ratios

Down payments for equipment financing typically range from 10% to 20% of the equipment's purchase price, though some lenders offer 100% financing for borrowers with excellent credit and strong financials. Larger down payments reduce monthly payments, lower interest rates, and improve approval odds.

Loan-to-value (LTV) ratios represent the percentage of equipment value the lender will finance. New equipment typically qualifies for LTV ratios of 80-100%, while used equipment may be limited to 70-90% depending on age, condition, and resale value. Equipment with strong resale markets (such as trucks, excavators, and medical equipment) qualifies for higher LTV ratios than specialized equipment with limited secondary markets.

Equipment Type and Condition

Lenders evaluate the equipment's type, condition, age, and resale value when determining approval and terms. New equipment from reputable manufacturers qualifies for the best rates and terms because it has predictable value and low risk of immediate failure. Used equipment faces more scrutiny, with lenders requiring appraisals and inspections to verify condition and value.

Equipment age limits vary by lender and equipment type. Most lenders won't finance equipment more than 10 years old, and many prefer equipment under 5 years old. Technology equipment faces stricter age limits (typically 3-5 years) due to rapid obsolescence, while heavy machinery and vehicles may qualify for financing up to 10 years old if well-maintained.

Specialized equipment with limited resale markets may face higher rates or lower LTV ratios because lenders have difficulty recovering value if you default. Conversely, equipment with strong secondary markets (construction equipment, trucks, medical devices) qualifies for better terms because lenders can easily resell it if necessary.

The Equipment Financing Application Process

Quick Answer: The application process takes 1-5 days and involves identifying equipment needs, obtaining supplier quotes, applying with lenders (providing business financials, credit authorization, equipment specifications), receiving approval, and closing. Most lenders offer online applications with same-day decisions for straightforward requests. Funding occurs within 1-3 days of approval.

Step 1: Identify Equipment Needs and Obtain Quotes

Before applying for financing, clearly identify the equipment you need, including specific make, model, features, and specifications. Research suppliers and obtain detailed quotes showing equipment cost, delivery fees, installation charges, and any additional costs. Having specific quotes demonstrates to lenders that you've done your homework and know exactly what you need.

Consider whether you need new or used equipment. New equipment offers warranties, the latest technology, and easier financing, but costs more. Used equipment saves money upfront but may require more maintenance and faces stricter financing terms. Evaluate the equipment's expected useful life, maintenance costs, and resale value when making this decision.

Step 2: Choose Your Financing Source

Equipment financing is available from multiple sources, each with different advantages. Banks and credit unions offer competitive rates (6-15%) but have stricter qualification requirements and slower approval (3-7 days). Equipment dealers and manufacturers often provide financing directly, offering convenience and promotional rates but potentially higher costs. Online lenders provide fast approval (1-2 days) and flexible qualification standards but charge higher rates (12-30%).

Consider applying with 2-3 lenders simultaneously to compare offers. Each lender has different underwriting standards, rate structures, and equipment preferences. Multiple applications increase your chances of approval and may result in better terms through competition. Most lenders perform soft credit pulls during initial evaluation, which don't affect your credit score.

Step 3: Complete the Application

Equipment financing applications require less documentation than working capital loans because the equipment serves as collateral. Typical requirements include business information (legal name, tax ID, address, ownership structure), personal information for owners with 20%+ ownership (Social Security number, address, credit authorization), financial information (1-2 years of business tax returns, recent bank statements, profit and loss statement), and equipment information (supplier quote, equipment specifications, intended use).

Many lenders offer online applications that can be completed in 10-20 minutes. Be prepared to explain how the equipment will be used and how it will generate revenue or reduce costs. Lenders want to see that the equipment investment makes business sense and will improve your ability to repay the loan.

Step 4: Underwriting and Approval

Once you submit your application, the lender evaluates your creditworthiness, business financials, and the equipment's value. For straightforward applications (strong credit, established business, new equipment from reputable manufacturer), approval can occur within hours. More complex situations (marginal credit, used equipment, specialized machinery) may require 2-5 days for underwriting.

The lender may request additional documentation such as equipment appraisals for used equipment, proof of insurance, or detailed financial projections showing how the equipment will improve business performance. Respond promptly to all requests to avoid delays.

If approved, you'll receive a commitment letter outlining loan amount, interest rate, term, monthly payment, down payment requirement, and any conditions that must be met before closing. Review the terms carefully and compare multiple offers if you applied with several lenders.

Step 5: Closing and Equipment Delivery

After accepting the loan terms, you'll complete closing documents including the loan agreement, security agreement granting the lender a lien on the equipment, UCC-1 financing statement filed with your state, and proof of insurance covering the equipment's full value. Most lenders require comprehensive insurance naming them as loss payee.

You'll make your down payment, and the lender will pay the equipment supplier directly. Once payment is confirmed, the supplier delivers and installs the equipment. You take possession immediately and begin making monthly payments according to the loan schedule. The lender maintains a lien on the equipment until you pay off the loan, at which point they release the lien and you own it free and clear.

Equipment Financing Costs and Fees

Quick Answer: Equipment financing costs include interest (6-30% APR depending on credit and equipment), origination fees (0-5% of loan amount), documentation fees ($100-$500), UCC filing fees ($25-$100), and insurance (typically 1-3% of equipment value annually). Total upfront costs typically range from 1-7% of the loan amount. Monthly payments are tax-deductible, and Section 179 allows immediate deduction of up to $1.16 million in equipment purchases.

Interest Rates

Equipment financing interest rates vary widely based on creditworthiness, time in business, equipment type, and whether the equipment is new or used. Borrowers with excellent credit (720+) and established businesses (3+ years) can secure rates as low as 6-10% for new equipment. Average credit (650-719) typically results in rates of 10-20%, while poor credit (below 650) may face rates of 20-30% or require alternative lenders.

New equipment qualifies for lower rates than used equipment because it has predictable value, lower failure risk, and better resale potential. The difference can be 3-10 percentage points, with new equipment at 8-15% and comparable used equipment at 15-25%. Equipment type also affects rates, with vehicles and standard machinery qualifying for better rates than specialized or custom equipment.

Most equipment loans offer fixed interest rates, providing payment stability and making budgeting easier. Some lenders offer variable rates tied to prime rate or LIBOR, which can start lower but fluctuate over time. Fixed rates are generally preferable unless you plan to pay off the loan quickly.

Origination Fees and Closing Costs

Origination fees cover the lender's cost of processing and underwriting your loan. These fees typically range from 0% to 5% of the loan amount, with most lenders charging 1-3%. Some lenders, particularly online lenders and equipment dealers, charge no origination fees but build the cost into higher interest rates.

Documentation fees cover the cost of preparing loan documents, filing UCC-1 financing statements, and processing paperwork. These fees typically range from $100 to $500 and are usually paid at closing. UCC filing fees vary by state but typically range from $25 to $100.

Some lenders charge application fees ($50-$200) to cover initial credit checks and evaluation, though many lenders have eliminated these fees to remain competitive. Be wary of lenders charging excessive upfront fees, as this may indicate predatory lending practices.

Insurance Requirements

Lenders require comprehensive insurance covering the equipment's full replacement value, with the lender named as loss payee. This ensures that if the equipment is damaged, destroyed, or stolen, the insurance proceeds pay off the loan. Insurance costs vary by equipment type but typically range from 1% to 3% of equipment value annually.

Some lenders offer insurance through their own programs or partners, which may be convenient but not always the best value. Shop around for insurance quotes from multiple providers to ensure competitive rates. Your existing business insurance provider may offer equipment coverage at competitive rates.

Tax Benefits of Equipment Financing

Equipment financing offers significant tax advantages that reduce the effective cost of borrowing. Interest payments are fully tax-deductible as business expenses, reducing your taxable income. For a business in the 25% tax bracket, a $10,000 interest payment saves $2,500 in taxes, effectively reducing the interest cost by 25%.

Section 179 of the tax code allows businesses to immediately deduct up to $1.16 million in equipment purchases (as of 2024) rather than depreciating them over multiple years. This provides substantial first-year tax savings. For example, purchasing $100,000 in equipment and claiming the full Section 179 deduction saves $25,000 in taxes for a business in the 25% tax bracket. Investopedia provides detailed guidance on Section 179 deductions and qualification requirements.

Bonus depreciation allows businesses to deduct an additional percentage of equipment costs in the first year beyond Section 179 limits. As of 2024, bonus depreciation is 60% of eligible equipment costs, though this percentage is scheduled to phase down in coming years. Combined with Section 179, these tax benefits can significantly reduce the after-tax cost of equipment purchases.

Advantages and Disadvantages of Equipment Financing

Advantages

Preserves Working Capital: Equipment financing allows you to acquire necessary equipment without depleting cash reserves. This preserves working capital for inventory, payroll, marketing, and other operational needs, improving financial flexibility and reducing the risk of cash flow problems.

Easier Approval Than Unsecured Loans: Because the equipment serves as collateral, lenders face less risk and are more willing to approve borrowers with limited credit history, shorter time in business, or lower credit scores. Approval rates for equipment financing are significantly higher than for working capital loans.

Fixed Monthly Payments: Most equipment loans offer fixed interest rates and fixed monthly payments, making budgeting predictable and protecting you from interest rate increases. You know exactly what you'll pay each month for the life of the loan.

Tax Benefits: Interest payments are tax-deductible, and Section 179 allows immediate deduction of up to $1.16 million in equipment purchases. These tax benefits can reduce the effective cost of equipment by 20-40% depending on your tax bracket.

Matches Payments to Equipment Life: Loan terms are structured to match the equipment's useful life, ensuring you're not making payments on obsolete or worn-out equipment. This alignment improves cash flow and ensures the equipment generates revenue throughout the loan term.

Fast Approval and Funding: Equipment financing typically offers much faster approval (1-5 days) than SBA loans (60-90 days) or conventional business loans (2-4 weeks). This speed allows you to acquire equipment quickly when opportunities arise or when business needs demand immediate action.

Disadvantages

Equipment Serves as Collateral: If you default on payments, the lender can repossess the equipment, disrupting your business operations. This risk is particularly concerning for equipment critical to your core business operations, as losing it could force you to cease operations temporarily or permanently.

Higher Interest Rates Than Some Alternatives: While equipment financing rates are competitive, they're typically higher than SBA loans (6-13%) or conventional bank loans (6-12%) for borrowers with excellent credit. The convenience and accessibility of equipment financing comes at a cost.

Down Payment Required: Most lenders require down payments of 10-20%, which can be substantial for expensive equipment. A $500,000 piece of equipment may require a $50,000-$100,000 down payment, which can strain cash flow for growing businesses.

Equipment Depreciation: Equipment loses value over time, and you may owe more than the equipment is worth, particularly in the early years of the loan. If you need to sell the equipment before paying off the loan, you may not receive enough to cover the outstanding balance.

Restrictions on Equipment Use: Loan agreements may restrict how you use the equipment, where you can move it, and whether you can modify or sell it. These restrictions limit flexibility and may prevent you from adapting to changing business needs.

Alternatives to Equipment Financing

While equipment financing is often the best option for acquiring business equipment, consider these alternatives:

Cash Purchase: If you have sufficient cash reserves, purchasing equipment outright avoids interest costs and provides immediate ownership. However, this depletes working capital and may leave you vulnerable to cash flow problems. Cash purchases make sense for inexpensive equipment or when you have excess cash earning minimal returns.

Business Line of Credit: A general business line of credit provides flexible access to capital for equipment and other business needs. Interest rates (8-20%) are typically higher than equipment loans, but you have more flexibility in how you use the funds. Lines of credit work well for multiple small equipment purchases or when you need flexibility to address various business needs.

SBA 504 Loans: For large equipment purchases ($125,000+), SBA 504 loans offer very competitive rates (6-9%) and long terms (10-20 years). However, the application process is lengthy (60-90 days) and documentation requirements are extensive. 504 loans work best when you're purchasing expensive equipment and have time to complete the application process.

Manufacturer Financing: Many equipment manufacturers offer financing directly or through captive finance companies. These programs often feature promotional rates (0-5% for qualified buyers) and convenient application processes. However, you're limited to that manufacturer's equipment, and promotional rates may only apply to select models or time periods.

Vendor Financing: Equipment dealers may offer financing directly, often with flexible terms and fast approval. Rates may be higher than bank financing, but the convenience and dealer relationships can provide value. Vendor financing works well when you have an established relationship with a dealer or when you need equipment immediately. Fundera offers a comprehensive comparison of equipment financing alternatives.

Tips for Equipment Financing Success

Shop Around for Best Rates: Equipment financing rates and terms vary significantly between lenders. Apply with 2-3 lenders including a bank, an online lender, and the equipment dealer or manufacturer to compare offers. Even a 2-3 percentage point rate difference can save thousands of dollars over the loan term.

Consider Total Cost, Not Just Monthly Payment: A longer loan term reduces monthly payments but increases total interest paid. A $100,000 equipment loan at 10% costs $21,247 in interest over 5 years but $39,322 over 7 years. Choose the shortest term you can comfortably afford to minimize total costs.

Negotiate Equipment Price First: Negotiate the best possible equipment price before discussing financing. Dealers may inflate prices when financing is involved, knowing buyers focus on monthly payments rather than total cost. Lock in your equipment price, then shop for the best financing separately.

Understand Lease vs. Loan Trade-offs: Leases offer lower monthly payments and easier upgrades but cost more over time and don't result in ownership. Loans have higher monthly payments but build equity and cost less long-term. Choose based on whether you need the latest equipment (lease) or plan to use equipment for its full useful life (loan).

Maximize Tax Benefits: Work with your accountant to maximize Section 179 deductions and bonus depreciation. Timing equipment purchases strategically (before year-end) can provide immediate tax benefits. Ensure you understand how to claim these deductions properly to avoid IRS issues.

Maintain Equipment Properly: Well-maintained equipment lasts longer, operates more efficiently, and retains value better. Follow manufacturer maintenance schedules, address problems promptly, and keep detailed maintenance records. This protects your investment and ensures the equipment generates revenue throughout the loan term.

Consider Equipment Resale Value: Some equipment holds value well (trucks, excavators, medical devices) while other equipment depreciates rapidly (computers, specialized machinery). Factor resale value into your purchase decision, as equipment with strong resale markets provides more flexibility if your business needs change.

Frequently Asked Questions

Can startups get equipment financing? Yes, startups can qualify for equipment financing, particularly if they have strong personal credit (680+), substantial down payments (20-30%), and are purchasing equipment with high resale value. Some lenders specialize in startup equipment financing and focus on the equipment's value rather than operating history.

What credit score do I need for equipment financing? Most lenders accept credit scores of 600+, though rates improve significantly with higher scores. Scores of 680+ qualify for the best rates (6-15%), scores of 600-679 face rates of 15-25%, and scores below 600 may see rates of 25-30% or require alternative lenders.

How long does equipment financing approval take? Most lenders provide decisions within 1-5 days, with many offering same-day approval for straightforward applications. Funding typically occurs within 1-3 days of approval. This is much faster than SBA loans (60-90 days) or conventional business loans (2-4 weeks).

Can I finance used equipment? Yes, most lenders finance used equipment, though rates are typically 3-10 percentage points higher than new equipment and LTV ratios are lower (70-90% vs. 80-100%). Lenders typically won't finance equipment more than 10 years old, and technology equipment faces stricter age limits (3-5 years).

What happens if I want to sell financed equipment? You must pay off the loan before selling financed equipment, as the lender holds a lien on it. Some lenders allow you to sell the equipment and use the proceeds to pay off the loan, with any excess going to you. Contact your lender before attempting to sell financed equipment.

Is equipment financing tax-deductible? Yes, interest payments on equipment loans are fully tax-deductible as business expenses. Additionally, Section 179 allows immediate deduction of up to $1.16 million in equipment purchases, and bonus depreciation allows additional first-year deductions. These tax benefits can reduce the effective cost of equipment by 20-40%.

Can I pay off equipment financing early? Most equipment loans allow early payoff without penalties, though some lenders charge prepayment penalties (typically 1-3% of the remaining balance). Review your loan agreement carefully to understand prepayment terms before signing.

Conclusion

Equipment financing provides a practical, accessible way for businesses to acquire the machinery, vehicles, technology, and other equipment they need to operate and grow. By spreading costs over time and using the equipment itself as collateral, businesses can preserve working capital while gaining immediate access to revenue-generating assets.

The variety of equipment financing options—loans, leases, and lines of credit—ensures businesses can find solutions matching their specific needs, whether they're purchasing a single piece of equipment or building an entire fleet. Fast approval times (1-5 days) and accessible qualification requirements (600+ credit score, 1-2 years in business) make equipment financing one of the most practical forms of business credit.

Tax benefits further enhance the value of equipment financing. Interest deductions, Section 179 deductions, and bonus depreciation can reduce the effective cost of equipment by 20-40%, making financed equipment purchases more affordable than they initially appear. These tax advantages, combined with competitive interest rates and terms matching equipment useful life, create compelling economics for businesses of all sizes.

The key to success is understanding your options, shopping around for the best terms, and choosing financing structures that align with your business needs and equipment usage patterns. Whether you're a construction company purchasing excavators, a restaurant upgrading kitchen equipment, a medical practice acquiring diagnostic devices, or a manufacturer investing in production machinery, equipment financing can help you acquire the tools you need to succeed.

Take the time to evaluate your equipment needs, compare multiple financing offers, and work with lenders who understand your industry and equipment type. With proper planning and the right financing partner, you can acquire the equipment your business needs while maintaining healthy cash flow and positioning yourself for long-term growth.

## Frequently Asked Questions