Free late fee calculators, and what free tools cannot do

A free late fee calculator works out interest and any fixed compensation on an overdue invoice: the amount, times the annual rate, times days overdue, divided by 365. It will not apply the fee, raise the invoice, send it, or keep it accurate as interest accrues daily. That part is what gets you paid.

Calculate it now

On an £850 invoice 30 days overdue under the UK statutory rate of 11.75%, you are owed £8.21 in interest plus £40 in fixed compensation, a total of £48.21 growing by 27p a day.

Pick your market, enter your own invoice, and the calculator shows what is owed today and what each further day adds.

Written out, so you can check the numbers.

An invoice of £850, 30 days overdue, under the UK statutory rate of 11.75% (Bank of England base rate plus 8%), with the £40 fixed compensation that applies to invoices under £1,000.

• Interest: £8.21. That is £850 × 11.75% × 30 ÷ 365.
• Fixed compensation: £40.00. A one-off sum, not a daily charge.
• Total owed on the charge: £48.21, growing by 27p a day.

Which calculator to use

The one above handles a single invoice in eight markets. For anything more, use the right specialist tool.

All three are free, with no sign-up. The full set of receivables tools is at paidnice.com/calculators.

What a free calculator cannot do

Every calculator on the internet, including ours, stops at the same place. It gives you a number and does nothing with it.

That is not a criticism of calculators. It is what they are. The problem is that the calculation was never the hard part.

The consistency problem

What separates businesses that collect on late fees is not the rate or the wording. It is whether the charge appears on every overdue invoice or only on the ones somebody got around to. A fee that shows up sometimes is read, correctly, as negotiable.

Your customer's accounts payable team processes thousands of invoices, and they learn quickly which suppliers have a system and which have a person who occasionally gets annoyed. Only the first group gets paid earlier. Consistent charging is also what shows up in your average wait for payment.

A good late fee policy applied when someone remembers collects less than a mediocre one applied every single time. Consistency is the mechanism, not the rate.

Which is the honest reason a calculator is not enough. Doing this by hand means someone sits down every month, works out the interest on each overdue invoice, raises each fee, sends each email, and then reverses the ones that get paid. In my experience that job survives a couple of months before something more urgent takes the morning.

One invoice, all the way through

Take the £850 above and follow it to the end, because the calculation is step one of five.

1. Calculate. £8.21 interest plus £40 compensation. Done above. Decide first whether the charge attaches to the invoice or the balance, in invoice late fee or statement interest, and whether it compounds, in compound or simple interest.
2. Raise it as a separate invoice, not a line on the original, with the tax rate set explicitly. Interest and UK compensation are outside the scope of VAT, which is not the same as zero rated.
3. Tell the customer, itemised, with the deadline that cancels the charge if the original is settled. Templates are in how to tell a customer you are charging a late fee.
4. Show it on the statement, recalculated on the day it is sent rather than the day it was raised. See late payment interest on customer statements.
5. Waive it when the original invoice is paid, using a credit note so the record survives. See waiving a late payment fee.

Five steps, on every overdue invoice, every month. That is the actual job.

What your market allows

The rate you can charge depends on whether your market gives you a statutory right or leaves it to your contract, and that split runs through all eight markets below.

In the UK and the EU the right is statutory and automatic. You can charge whether or not your contract mentions it. Almost everywhere else the right is contractual, so the clause has to exist before the invoice does, and a court would decide any dispute under contract law.

Country detail is in how much can I charge for late fees, and the US caps are in late fee laws by US state. In a contractual market the clause has to exist first, so start with payment terms and conditions templates and late fee policy wording examples.

How Paidnice does this, and how simple it is

Paidnice does all five steps above, on every overdue invoice, without anyone deciding to.

• The fee calculates and applies itself on every overdue invoice in a customer group, so consistency stops depending on somebody's Monday morning.
• Set the rate the way your market works. Turn on the Bank of England base rate and Paidnice applies base plus your percent, tracking the base rate so you never charge last period's figure. Under the Act the rate is set by the six-month period in which the invoice fell overdue. Outside the UK, set your own rate and add a fixed or admin charge.
• The customer is told automatically, with the figures itemised, and the charge appears on their next statement recalculated to that day.
• Removing it is a void or a credit note on that one fee invoice, and unallocated credit notes are netted off before the charge is worked out.

Setting it up is one policy on one customer group, and you can leave it in draft for the first month to see what it would have raised before anything goes out. Plans start at £49 a month, with no per-seat fees.

Common questions

Is there a free late fee calculator?
Yes, several on this page, with no sign-up. Use the one above for a single invoice in eight markets, the UK statutory calculator for the current Bank of England rate, or the advanced calculator for several invoices at once.

How do I calculate a late payment fee?
Interest is the overdue amount times the annual rate times days overdue divided by 365. Add any fixed compensation or admin fee your terms or your market allow. On £850 at 11.75% for 30 days that is £8.21, plus £40 in the UK, so £48.21.

Is free late fee software available?
Free tools calculate. They do not apply the charge to your ledger, notify the customer, keep the figure current, or handle the waive. That gap is the reason most businesses with a calculator still do not collect late fees.

Why is the fixed fee bigger than the interest?
On small invoices it usually is, and that is intentional. The UK compensation sum exists to cover the cost of recovering the debt, which does not scale with the invoice.

Do I need to sign up to use these?
No. All the calculators linked here are free and open.

Written by

Denym Bird

Co-founder & CEO of Paidnice

Denym is a software entrepreneur and writes about accounts receivables management for small business.

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