Late Payment Interest Calculator

Calculate interest and admin fees on overdue invoices using annual, monthly, or fixed rate methods. Supports compound interest and batch processing.

Calculator Settings
Configure your interest calculation method and rates

Daily rate: 0.0329%

Interest compounds monthly on previously accrued interest

Fixed fee per late invoice for administrative costs

Results Summary
Total Amount Due
$1,009.86
Original Amount
$1,000.00
Total Interest
$9.86
Invoices
1
Avg Days Overdue
30 days
Daily Interest Rate
0.0329%
Invoice Details
Add your overdue invoices to calculate total interest
30 days
$9.86
$1,009.86

Important Notice

This calculator provides an estimate for late payment interest and admin fees based on your chosen parameters. Always ensure your late payment terms comply with local regulations and are clearly communicated to customers before extending credit.

How Late Payment Interest Works

Annual Rate Method

Calculates daily interest by dividing the annual rate by 365, then multiplying by days overdue. Most common for B2B invoices.

Interest = Amount × (Rate ÷ 365) × Days

Monthly Rate Method

Applies a monthly percentage rate proportionally based on days overdue. Common for consumer credit and retail.

Interest = Amount × Rate × (Days ÷ 30)

Fixed Percentage

Charges a one-time percentage fee regardless of how long the payment is overdue. Simple and easy to communicate.

Fee = Amount × Fixed Rate

Best Practices for Late Payment Policies

Clear Communication

State late payment terms clearly on all invoices, contracts, and payment reminders.

Reasonable Rates

Use industry-standard rates (1-2% monthly) that are enforceable in your jurisdiction.

Grace Periods

Consider offering a brief grace period before applying interest to maintain customer relationships.

Consistent Enforcement

Apply late fees consistently to all customers to avoid discrimination claims.

Legal Compliance

Verify maximum allowable rates and disclosure requirements in your jurisdiction.

Automated Tracking

Use invoicing software to automatically calculate and apply late fees.

Frequently Asked Questions

The most common formula is: Invoice Amount × (Annual Interest Rate ÷ 365) × Days Overdue. For example, a $1,000 invoice at 12% annual interest that's 30 days late would accrue: $1,000 × (0.12 ÷ 365) × 30 = $9.86 in interest.

Automate Late Payment Tracking

PineBill automatically tracks overdue invoices, calculates late fees, and sends payment reminders so you get paid faster.