How do I calculate how much invoice finance funding my business could get
Working out how much invoice finance you can access is straightforward once you know the key figures involved. This guide walks you through the calculation, explains what lenders look at, and shows you how to get a realistic picture of the funding available to your business.
What is invoice finance and how does it work?
Invoice finance (also called invoice factoring or supply chain financing) lets you borrow money against unpaid invoices. Instead of waiting 30, 60 or 90 days for customers to pay, you can access a percentage of that invoice value now. You'll pay interest and fees, but you get cash flowing through your business immediately.
- Invoice factoring - a lender buys your invoice at a discount and handles customer collection
- Invoice discounting - you keep control of customer relationships and repay when invoices are paid
- Supply chain financing - your suppliers get paid early by a lender, and you pay the lender back on normal terms
All three options are regulated by the FCA in the UK, and reputable lenders are usually members of the NACFB (National Association of Commercial Finance Brokers).
The basic calculation: your funding potential
The amount you can borrow depends mainly on the value of your unpaid invoices. Here's the simple formula most lenders use.
- Step 1: Add up your outstanding invoices - List all unpaid invoices that are less than 90 days old (most lenders won't fund older invoices)
- Step 2: Multiply by the advance rate - Lenders typically advance 80% to 95% of invoice value. For example, if you have £50,000 in invoices and the advance rate is 85%, you can borrow £42,500
- Step 3: Deduct fees and interest - Most lenders charge 1% to 3% per month on the amount you borrow, plus a one-off arrangement fee (usually £200 to £1,000). These reduce your net cash
Your maximum borrowing amount will never exceed the total value of your eligible invoices.
Key factors lenders assess
Beyond the invoice value itself, lenders look at several other things when deciding how much to lend and at what cost.
- Customer credit quality - If your invoices are from well-known, reliable companies, you'll qualify for higher advance rates. Invoices from new or risky customers get lower rates
- Invoice age - Fresh invoices (under 30 days old) are worth more than those approaching 90 days. Most lenders won't touch invoices over 120 days
- Your business turnover - Lenders want to see at least £50,000 to £100,000 annual turnover, though some accept smaller businesses
- How long you've been trading - Established businesses (2+ years) get better terms than startups. New businesses may struggle to access invoice finance at all
- Your payment history - If you've defaulted on previous finance or have County Court Judgments, lenders will offer less or decline you
The strongest businesses (steady customers, high turnover, clean payment history) can sometimes access 90-95% of invoice value at competitive rates.
Worked example: calculating your own funding
A typical small business scenario
Let's say you run a manufacturing business with these invoices: three invoices of £10,000 each to a major supermarket chain (20 days old), two invoices of £8,000 each to an independent retailer (35 days old), and one invoice of £5,000 to a new customer (50 days old). Your total eligible invoices are £59,000. The lender offers 85% advance on the supermarket invoices (they're a grade-A customer), 80% on the independent retailer, and 70% on the new customer. That gives you: (£30,000 x 0.85) + (£16,000 x 0.80) + (£5,000 x 0.70) = £25,500 + £12,800 + £3,500 = £41,800. With a 2% monthly fee on £41,800, you'll pay roughly £836 per month. Your net drawdown is around £41,000 after initial fees.
Fees and charges you need to know about
Invoice finance isn't free, and understanding the full cost helps you work out if it's worth it for your business.
- Monthly interest or service charge - Usually 1% to 3% of the amount you've borrowed, calculated daily. A £40,000 facility at 2% per month costs £800
- Set-up or arrangement fee - A one-off charge of £300 to £1,500 when you first sign up
- Discount fee (for factoring) - On top of monthly charges, some factoring lenders take a small percentage when they collect the invoice (typically 0.5% to 2%)
- Compliance or administration fee - Some lenders charge £50 to £200 per month to manage invoices and customer accounts
- Early settlement or early repayment fee - Rarely charged by modern lenders, but check the small print
Always ask for a worked example showing exactly what you'll pay on your expected borrowing level.
How to improve your funding amount
If the initial calculation shows you could access more, here are practical steps to increase your borrowing capacity.
- Increase your invoice base - More invoices means more collateral. Winning new customers or larger orders directly grows your potential funding
- Improve customer quality - Target invoices from blue-chip companies or long-standing clients. Lenders will advance higher percentages against these
- Invoice sooner - Send invoices immediately on delivery rather than waiting. Fresher invoices are worth more
- Reduce invoice age - Chase late payments and improve your collection terms. Invoices under 30 days get better advance rates
- Build a clean track record - If you're new to invoice finance, making all repayments on time for 3-6 months often leads to a lender increasing your limit
- Diversify your customer base - Heavy reliance on one or two customers limits your funding. Spread risk by adding more invoice sources
Even small improvements in invoice quality or speed can unlock thousands of pounds in additional funding.
How Spark Finance can help
Calculating your own funding figure is a good starting point, but getting a professional assessment takes the guesswork out. Spark Finance is FCA-authorised (FRN 958123) and works with over 100 lenders across the UK market. We can match your business to the right lender based on your industry, turnover, customer base, and credit profile. Best of all, our initial eligibility check is free and carries no obligation - we won't run a hard credit check at that stage, so there's no impact on your credit file. Simply share your recent invoices and accounts, and we'll give you a realistic picture of what you could access and at what cost. Many business owners are surprised at how much funding is available to them once they've had a professional review.
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Frequently asked questions
What's the minimum amount of invoices I need to access invoice finance?
Most lenders require at least £10,000 to £25,000 in eligible invoices to make the arrangement worthwhile. However, some specialist lenders will work with smaller amounts. Your annual business turnover also matters - lenders typically want to see at least £50,000 to £100,000 per year.
Can I use invoices from any customer, or do they have to be creditworthy?
You can use invoices from any customer, but the advance rate (how much you can borrow) depends on their creditworthiness. Invoices from blue-chip companies might get you 90% advance, while invoices from newer or riskier customers might only get 70%. Very high-risk customers may not be fundable at all.
How quickly can I get the money once I've applied?
Once approved, most lenders can transfer funds within 24 to 48 hours. Some can do it same-day. The actual approval process typically takes 3 to 5 working days, depending on how quickly you provide documents like recent accounts and customer references.
Will getting invoice finance affect my credit score?
An initial eligibility check with no obligation won't show on your credit file at all. Once you formally apply and a lender does a full credit check, it will show as a hard inquiry but won't damage your score significantly. If you're approved and use the facility responsibly, maintaining repayments actually helps your credit history.
Important information: Spark Finance Limited is authorised and regulated by the Financial Conduct Authority (FRN 958123). We are a credit broker, not a lender. This guide is for informational purposes only and does not constitute financial advice. Think carefully before securing debts against property or assets. Your business may be at risk if you do not keep up repayments on a debt or other commitment entered into in relation to it.