💳 Billing & Finance · Free

Late Fee & Interest Calculator

Calculate late payment fees and simple interest charges on overdue invoices. Free late fee calculator for service businesses.

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Original invoice€1000.00
Interest charges€6.58
Total amount due€1006.58

⚠️ Check your country's late payment laws before applying interest charges. EU Late Payment Directive allows up to ECB rate + 8%.

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Frequently asked questions

How do I calculate simple interest on a late invoice?

Interest = Principal × Rate × Time. For example: €1,000 at 8% annual rate for 30 days: €1,000 × 0.08 × (30/365) = €6.58.

What late fee rate is standard?

Common rates are 1.5–2% per month or 8–10% annually. The EU Late Payment Directive allows up to 8% above the ECB reference rate for B2B invoices.

Should I always charge late fees?

Have a clear late payment policy in your terms. For long-term clients, a warning first is often better for the relationship. Automated reminders prevent most late payments.