---
title: "Free late fee calculators, and what free tools cannot do"
description: "Free tools work out a late fee or interest on an overdue invoice. None applies it. Which free calculator to use, the UK formula, and where each free tool stops."
url: https://www.paidnice.com/blog/free-late-fee-calculator
---

# Free late fee calculators, and what free tools cannot do

Written by

Denym Bird
Expert verified

Co-founder & CEO of Paidnice

Denym surveyed free late fee calculators, covering the UK interest formula, which tool to pick, and where each one stops short of applying a fee to an invoice.

Reviewed by Ashley Schroder

Co-founder of Paidnice

Updated Nov 6, 2026 · 10 min

## Summary

Free late payment fee software calculates the fee or interest on an overdue invoice. Square Invoices adds a late fee to its invoices in the US and Canada; no free tool applies the charge in Xero or QuickBooks, chases it or keeps it current. On an £850 invoice 30 days overdue at the UK statutory rate the charge is £48.21.

- **Calculates for free:** The calculator on this page, the UK statutory interest calculator and the EU directive calculator work out interest and fixed compensation with no sign-up.
- **Applies automatically, paid:** Paidnice applies late fees and interest automatically in Xero and QuickBooks Online: free sign-up, no card, first 20 actions free, then from £49 or $69 a month.
- **The UK formula:** 8% above the Bank of England base rate, 11.75% for invoices overdue by 31 December 2026 (3.75% base rate on 30 June 2026), plus £40, £70 or £100 fixed compensation per invoice.

## 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.

What an overdue invoice is costing you

Market

Interest basis

Overdue amount
Days overdue

Interest rate (% per year)
Fixed or admin fee

#### Total now owed on the charge

£48.21
£8.21 interest, plus £40.00 fixed fee

#### What the delay costs them per day

£0.27
Accruing today, at the basis selected

Simple£8.21Compounded monthly£8.21Compounded annually£7.80

UK statutory: Bank of England base rate plus 8%, fixed in six-month blocks, plus £40, £70 or £100 by invoice size. Verify the current base rate at bankofengland.co.uk.

For several invoices at different ages, or to compare calculation methods on one debt, use [the full calculator](https://www.paidnice.com/late-payment-interest-calculator).

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**.

💡 Paidnice insight

Look at the split. On this invoice the fixed charge is **83% of the late payment charge**, and the interest is 17%. On small invoices the fixed compensation does almost all the work. Under a few thousand, the fixed sum is the part most people forget to claim.

## What is a late fee (and what is it not)?

**A late fee is a charge a seller adds to an invoice when the customer pays after the due date, as a flat amount, a percentage or interest.** It is also called a late payment fee. See the [definition of a late fee](https://www.paidnice.com/dictionary/late-fee).

- **A late fee is not only interest.** Interest grows each day an invoice stays unpaid. A flat fee or the UK fixed compensation of £40, £70 or £100 does not grow with time.
- **A calculated late fee is not an applied late fee.** A calculator gives you a number. The fee exists only once it is on the invoice and the customer has been told.

This matters because a free calculator answers what is owed today. The next sections show the UK formula and where each free tool stops.

## The UK late payment interest formula

UK statutory interest is 8% above the Bank of England base rate, plus fixed compensation of £40, £70 or £100 per invoice. With the 3.75% base rate fixed on 30 June 2026, the rate is 11.75% for invoices overdue by 31 December 2026.

UK statutory late payment charge
Interest = amount × (base rate + 8%) × days overdue ÷ 365, plus £40, £70 or £100

- **Rate:** Bank of England base rate plus 8%. The [base rate was 3.75% on 30 June 2026](https://www.bankofengland.co.uk/monetary-policy/the-interest-rate-bank-rate), so the statutory rate is 11.75% for invoices overdue by 31 December 2026. The base rate rose to 4% on 5 November 2026, which gives 12% for invoices that fall overdue from 1 January 2027 if it is still 4% on 31 December.
- **Which base rate:** the one in force on 30 June or 31 December, fixed for the following six months, under the [Late Payment of Commercial Debts Regulations 2002](https://www.legislation.gov.uk/uksi/2002/1675/article/4/made).
- **Fixed compensation:** [£40 under £1,000, £70 from £1,000 to £9,999.99, £100 from £10,000](https://www.gov.uk/late-commercial-payments-interest-debt-recovery/claim-debt-recovery-costs), per invoice, on top of the interest.

## What mistakes cost you money when you use a late fee calculator?

Three mistakes change the figure or leave it uncollected.

- **Counting the days from the invoice date.** On the £850 invoice above, on 30 day terms, 60 days since the invoice is 30 days overdue. Entering 60 gives £16.42 (£850 × 11.75% × 60 ÷ 365), double the £8.21 owed.*Fix: count the days from the due date.*
- **Typing the base rate as the rate.** UK statutory interest is the base rate plus 8%. Entering 3.75% gives £2.62 (£850 × 3.75% × 30 ÷ 365), £5.59 less than the £8.21 owed.*Fix: enter 11.75%, the base rate plus 8%.*
- **Stopping at the number.** 68% of businesses that start charging late fees get more invoices paid on time. For similar businesses that do not charge them, it is 52%.*Fix: raise the fee as an invoice and tell the customer.*Source: our analysis of invoice data from over 1,000 Paidnice customers. See [our late fee data](https://www.paidnice.com/blog/do-late-fees-work#pay-on-time).

## Which calculator to use

The calculator above handles one invoice in eight markets. The three below cover the current UK base rate, several invoices at once, and the EU directive.

UK statutory interest calculator
Use this when you need the current Bank of England base rate applied for you, and the £40, £70 and £100 compensation tiers picked by invoice size.

Open

Advanced late payment interest calculator
Use this when you have several invoices at different ages, or want to compare fixed, monthly and annual calculation methods on the same debt.

Open

EU late payment directive calculator
Use this for invoices inside the EU, where the ECB reference rate plus 8 percentage points and €40 minimum compensation apply, with country-specific rates.

Open

All three are free, with no sign-up. The full set of receivables tools is at [paidnice.com/calculators](https://www.paidnice.com/calculators).

## What can a free late fee calculator not do?

A free late fee calculator cannot apply the fee to your ledger, send it to the customer, keep the figure current as interest accrues, or see the other overdue invoices behind it. Every calculator, including ours, stops at the number.

It will not apply the feeNothing happens to your ledger. You still have to raise an invoice for the amount it just showed you.
It will not send anythingThe customer does not know. Somebody still has to write the email and press send.
It will not stay accurateInterest accrues daily, so the figure is out of date tomorrow and materially wrong in a fortnight.
It will not rememberIt works out one invoice, once. It has no idea there are another forty overdue behind it.

The table below shows where each free tool stops.

**A calculator cannot tell you which fee gets paid.** About 8 in 10 fixed late fees get paid. Only about 6 in 10 percentage-based fees do, and percentage fees are the ones waived most often.
Original dataSource: our analysis of invoice data from over 1,000 Paidnice customers. See our late fee data.

## Which free tools add late fees to invoices?

Square Invoices is the one free tool in this list that adds a late fee, on its own invoices in the US and Canada. The calculators give you the figure; the other free invoicing apps stop short of applying one.

| Tool | Cost | What it does |
| --- | --- | --- |
| **The calculator on this page** | Free, no sign-up | Interest and fixed fee on one invoice in eight markets, simple or compound, with the daily accrual |
| **UK statutory interest calculator** | Free, no sign-up | Base rate plus 8% and the £40, £70 or £100 tier, picked by invoice size |
| **Wave** | Free plan | No late fee feature on any plan; a fee is a line item you type on the invoice and resend |
| **Square Invoices** | Free plan | Adds a flat or percentage late fee to an invoice, with an optional grace period, for US and Canada sellers |
| **Invoice Ninja** | Free plan | A late fee amount or percent attached to its reminders; automatic reminders are on the paid plan |
| **Paidnice** | Free sign-up, no card, first 20 actions free, then from £49 or $69 a month | Applies late fees and interest automatically in Xero and QuickBooks Online, tells the customer, and shows the charge on the statement |

## The consistency problem

Businesses that collect on late fees put the charge on **every** overdue invoice, rather than the ones somebody got around to. A fee that shows up sometimes is read, correctly, as negotiable.

Consistent charging shows up in [your average wait for payment](https://www.paidnice.com/blog/dso-calculation-formula).

That is why a calculator is not enough. Manually, someone sits down every month, works out the interest on each overdue invoice, raises each fee, sends each email, and reverses the ones that get paid. That job usually survives a couple of months before something more urgent takes the morning.

## One invoice, all the way through

The £850 charge above is step one of four: calculate it, raise it, tell the customer, and waive it when the original invoice is paid.

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](https://www.paidnice.com/blog/invoice-late-fee-vs-statement-interest), and whether it compounds, in [compound or simple interest](https://www.paidnice.com/blog/compound-interest-on-overdue-invoices).
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](https://www.paidnice.com/blog/how-to-account-for-late-fees).
3. **Tell the customer**, itemized, with the deadline that cancels the charge if the original is settled, using the templates in [how to tell a customer you are charging a late fee](https://www.paidnice.com/blog/late-fee-email-to-customer). Then show it on the statement, recalculated on the day it is sent, as in [late payment interest on customer statements](https://www.paidnice.com/blog/late-payment-interest-on-statements).
4. **Waive it** when the original invoice is paid, using a credit note so the record survives. See [waiving a late payment fee](https://www.paidnice.com/blog/waiving-late-payment-fees).

## 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.

| Market | Basis | Typical rate |
| --- | --- | --- |
| **UK** | Statutory, automatic on B2B | Base rate plus 8%, plus £40, £70 or £100 per invoice |
| **EU** | Statutory, [Directive 2011/7/EU](https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=celex%3A32011L0007) | ECB reference rate plus at least 8 percentage points, which is [10.40% for the second half of 2026](https://www.ecb.europa.eu/stats/policy_and_exchange_rates/key_ecb_interest_rates/html/index.en.html), plus €40 minimum |
| **US** | Contractual, state usury caps | 1% to 1.5% a month |
| **Australia** | Contractual | No statutory rate. Around 10% a year is common practice |
| **New Zealand** | Contractual | No default in law. Set it in your terms |
| **Canada** | Contractual, provincial variation | State the annual equivalent rate |
| **South Africa** | Prescribed Rate of Interest Act | Prescribed rate, 10.50% from July 2026 and 10.75% from November 2026, set as repo plus 3.5% when gazetted |
| **Singapore** | Common law, older test retained | Genuine pre-estimate of loss |

**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.

Country detail is in [how much can I charge for late fees](https://www.paidnice.com/blog/how-much-can-i-charge-for-late-fees), and the US caps in [late fee laws by US state](https://www.paidnice.com/blog/late-fee-laws-by-all-us-states). For a contractual market, start with [payment terms and conditions templates](https://www.paidnice.com/blog/payment-terms-and-conditions-templates) and [late fee policy wording examples](https://www.paidnice.com/blog/late-fee-policy-wording-examples).

## How Paidnice does this, and how simple it is

[Paidnice](https://www.paidnice.com/late-fee-manager) does all four steps above, on every overdue invoice, without anyone deciding to. Customers see half as many late invoices in the first 30 days.

- **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, locked for each six-month period as the Late Payment Order sets it, or following the base rate as it changes. Outside the UK, set your own rate and add a fixed or admin charge.
- **The customer is told automatically**, with the figures itemized, 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 calculated.

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. Sign-up is free with no card, and the first 20 actions are free with no time limit. After that [plans start at £49 or $69 a month](https://www.paidnice.com/pricing), with no per-seat fees.

## Common questions

Short answers to the questions people ask alongside this calculator.

**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 calculators give you the figure, and Square Invoices can add a late fee to its own invoices in the US and Canada. Applying the charge in Xero or QuickBooks Online, telling the customer, keeping it current and handling the waive is paid automation. Paidnice has a free sign-up with no card, then plans from £49 or $69 a month.

**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.

## Paidnice features in this article

- [**Late fees and interest** Adds late fees and interest to overdue invoices when you turn them on.](https://www.paidnice.com/late-fees)
- [**Email and SMS reminders** Sends reminders by email and SMS on your schedule, each with a link to pay.](https://www.paidnice.com/email-sms-reminders)
- [**Customer statements** Sends branded customer statements on your schedule, with one button to pay.](https://www.paidnice.com/automated-customer-statements)

## About the editorial team

Written by Denym Bird Co-founder & CEO of Paidnice

Denym started Paidnice in 2022 after customers paying late left his own business short on payroll. He has led it to $1 billion collected on time across more than 1 million invoices, and writes about credit control, late fees and getting paid on Xero and QuickBooks.

Reviewed by Ashley Schroder Co-founder of Paidnice

Ashley is a co-founder and lead developer of Paidnice and has built accounting software for more than 10 years. He builds the ledger connections that put reminders, late fees and payments into Xero, QuickBooks and ERPs such as NetSuite and Business Central. Before Paidnice he co-founded A2X, ecommerce accounting software for Xero and QuickBooks.

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