Work out what to add to an overdue invoice: monthly interest prorated by days late, or a flat fee, with the new total and suggested wording. No signup.
Suggested invoice wording: “A late fee of 1.5% per month applies to balances unpaid after the due date.” Late-fee terms must be agreed before the invoice is overdue; local caps may apply.
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On Creator Pro ($8.99/mo) and Team, BillingOtter sends automatic payment reminders and can add an optional late fee for you. Every plan shows which invoices are paid, due or overdue.
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Most freelancers and small businesses charge 1–1.5% per month (12–18% per year) or a flat fee of $25–50. The key requirement: the late fee terms must be stated on the invoice or in your contract BEFORE the client is late — you generally can't add fees retroactively. Some regions cap interest rates, so check your local rules for large amounts.
Fee = invoice amount × monthly rate × (days late ÷ 30). A $1,500 invoice at 1.5% per month, 45 days late: 1500 × 0.015 × 1.5 = $33.75.
Their real power is preventive: invoices that state a late fee get paid noticeably faster. Pair the policy with automatic payment reminders — that combination is what actually moves the number of on-time payments.