B/Billable Toolkit
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Invoice Due Date & Late Fee Calculator

Check exactly when an invoice is due and what an overdue client owes you under your late-fee terms.

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Check what your contract or local law allows

Status

How it’s calculated

The due date is the invoice date plus the term in calendar days. The late fee is pro-rated daily from a monthly rate, counted from the day after the due date.

due date = invoice date + term days late fee = amount × monthly rate × (days overdue ÷ 30)

Worked example

A $2,400 invoice dated 19 September on Net 30 terms is due on 19 October. If it is paid 11 days late with a 1.5% monthly late fee, the fee is $13.20.

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Questions

What does Net 30 mean?

Payment is due 30 calendar days after the invoice date, including weekends.

Can I charge a late fee?

Usually only if it was agreed in your contract or stated on the invoice before the work. Rules differ by country, so check yours.

Doing these numbers every month? Accounting software can automate invoices, reminders and tax reports.

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