Calculate a Stated Late Fee on an Overdue Invoice
Enter the overdue principal, annual simple rate, days overdue and fixed fee. The calculator exposes interest and fixed components separately instead of hiding them in one demand amount.
Separate overdue interest and fixed fees
The default example applies eight percent simple annual interest for 45 overdue days.
- Simple overdue interest
- $49.32
- Principal plus calculated fee
- $5,049.32
- Interest per overdue day
- $1.10
Principal multiplied by annual rate and overdue days divided by 365, plus fixed fee.
Reproduce a fee already supported by the agreement
Calculate a stated simple late fee on a invoice from principal, annual rate, days overdue and any contractually supported fixed charge.
Keep the invoice trail described in freelance income recordkeeping and protect cash timing through the multiple-income planner.
Verify the term before calculating
Read the signed payment terms
Do not add a fee merely because an invoice is late.
Apply partial payments first
Interest should use the supported outstanding balance and period.
- Calculation method
- Principal multiplied by annual rate and overdue days divided by 365, plus fixed fee.
- Best used for
- Checking arithmetic after the contract and enforceability have been confirmed.
- Keep outside the result
- Compounding, partial payments, legal entitlement, tax treatment and collection costs.
Use the correct outstanding principal
Deduct supported payments and credits before applying the rate to the remaining balance.
Count the supported period
Record due date, grace period and calculation date so days overdue can be reproduced.
Keep collection evidence
Preserve invoice delivery, reminders, client responses and payment entries alongside the calculation.
Separate overdue interest and fixed fees in a worked example
The default example applies eight percent simple annual interest for 45 overdue days. Simple annual interest is applied to the outstanding principal for the entered overdue days, then the fixed fee is shown separately. Confirm the contract, due date, grace period, supported balance and applicable law before invoicing the result. Payments and credits reduce principal first.
- Outstanding invoice principal
- $5000
- Stated annual simple rate
- 8 %
- Days overdue
- 45
- Supported fixed late fee
- $0
Calculated late-fee total: $49.32
Confirm the agreement, applicable law, notices and outstanding balance before charging a fee.
- Simple overdue interest
- $49.32
- Principal plus calculated fee
- $5,049.32
- Interest per overdue day
- $1.10
Calculation rule: Principal multiplied by annual rate and overdue days divided by 365, plus fixed fee. Boundary: Compounding, partial payments, legal entitlement, tax treatment and collection costs.
Invoice late-fee questions
Does this make a late fee enforceable?
No. It only calculates terms already supported by the relevant agreement and law.
Does it compound interest?
No. The displayed method uses simple annual interest.
Can I add collection costs?
Only when a separate supported basis exists; they are excluded here.
Preserve the invoice, terms and collection timeline
Track salary, freelance, rental and business income with source-level records, cash timing, direct costs and a separate tax reserve.