Late fee calculator

The three ways late fees are charged

• Flat fee — a fixed amount once the due date passes (“$25 late fee after Net 30”). Simple and common on small invoices.
• One-time percentage — a single charge proportional to the invoice (“5% after 14 days late”). Scales with the debt, doesn't grow with time.
• Monthly interest — the professional standard: “1.5% per month on overdue balances” (18% a year), pro-rated by days. This calculator pro-rates daily: fee = amount × monthly rate × days/30.

What's typical — and what's enforceable

Across freelancing and B2B services, 1%–2% per month is the customary band; many jurisdictions also provide a statutory fallback. In the EU, the Late Payment Directive entitles businesses to reference-rate-plus-8% interest and a €40 minimum recovery cost on commercial debts. In the UK, statutory interest is 8% above the Bank of England base rate. In the US, state usury caps can limit contractual rates. The universal rule: a late fee is only enforceable if it was agreed before the work — which means it must appear on your invoice or contract terms, not for the first time on a reminder.

Put the term on the invoice, not in the argument

A line like “Payment due within 30 days. Overdue balances accrue interest at 1.5% per month.” in your invoice terms does two jobs: it makes the fee chargeable, and it quietly accelerates payment — clients triage invoices by consequence. Save it as a terms snippet in the invoice generator and it lands on every invoice automatically.

Using the demand line

When an invoice does go overdue, the generated sentence above states the facts — original amount, due date, days overdue, the term being applied, and the new total — in the neutral, factual tone that gets results. Paste it into the payment reminder generator, which drafts the full email around it in your choice of friendly, firm or final-notice register.

Frequently asked questions