Invoicing and Payment Calculators

Invoice Generator, Due Date Calculator and Late Payment Interest Tool

Getting paid, and knowing what arrives. Build an invoice and download it as a PDF, work out when net-30 actually falls due, calculate the interest you are entitled to charge on a late payment, and see exactly what Stripe or PayPal will deduct — and what to charge so the amount you want is the amount you receive.

Every Invoicing & Payments tool

Invoice Due Date Calculator

Exact Net-30, Net-60 and Net-90 deadlines with weekend rollover.

Invoice Generator

Type the details, download a clean PDF invoice. Nothing uploaded.

Late Payment Interest Calculator

Daily interest on an overdue invoice, plus the recovery charge.

Guides for common jobs

Name and brand a new business — Eight free tools that take a business from no name to a first invoice.

Producing the invoice

The invoice generator is a form that becomes a PDF. Your details, the client's, line items with quantity and rate, tax at whatever rate applies, payment terms and bank details — laid out cleanly and downloaded to your machine. Nothing is stored on a server; if you want to reuse your details, the browser can remember them locally on your own device. It is deliberately simple: one invoice, one page, no accounts, no templates to buy.

Due dates

"Net 30" means thirty days from the invoice date, but people disagree about whether that means calendar days, whether it lands on a weekend, and whether "end of month plus 30" is the same thing. The due-date calculator takes the invoice date and the terms, shows the resulting date, and rolls forward past weekends if you ask it to, so the date on the invoice is one you and the client will read the same way.

Late payment interest

In the UK and much of Europe, businesses have a statutory right to charge interest on overdue commercial invoices — a set margin above the central bank base rate, plus a fixed compensation amount by invoice size. The calculator applies the rate you enter to the days overdue and shows the interest and compensation due, so a chasing email can quote an exact figure.

Processor fees

The Stripe and PayPal calculators answer two questions. Forwards: if I charge this much, what lands in my account after the percentage and the fixed fee? Backwards: if I need this much to land, what do I charge? The backwards case is the one people get wrong — adding the fee percentage on top comes up short, because the fee is then charged on the larger amount too. The tools solve it properly and show the effective rate, which on small transactions is much higher than the headline percentage suggests. Fee rates are editable because they vary by country, card type and account.

Nothing you enter is transmitted

Client names, bank details and amounts stay in your browser. The PDF is generated on your device and downloaded directly; no copy exists anywhere else.