Calculator Inputs
Example Data Table
| Scenario | Invoice | Rate | Days Overdue | Method | Late Fee | Interest | Total Due |
|---|---|---|---|---|---|---|---|
| Standard reminder | $4,000.00 | 8.00% | 30 | Simple | $20.00 | $26.30 | $4,046.30 |
| Compounded balance | $9,500.00 | 12.00% | 60 | Daily compounding | $35.00 | $189.47 | $9,724.47 |
| Partial payment case | $12,500.00 | 12.00% | 40 | Monthly compounding | $35.00 | $118.98 | $11,178.98 |
The example rows illustrate typical outcomes only. Contract terms, local law, tax treatment, and allocation rules can change collectible amounts.
Formula Used
Simple interest: Interest = Balance × Annual Rate × (Days Overdue ÷ Day Count Basis)
Daily compounding: Balance = Principal × (1 + Annual Rate ÷ Basis)Days
Monthly compounding: Balance = Principal × (1 + Annual Rate ÷ 12)Days ÷ 30
Tax on interest: Tax = Gross Interest × Tax Rate
Total due: Remaining Invoice Balance + Gross Interest + Interest Tax + Late Fee
When a partial payment is entered, the calculator first grows the balance for the initial overdue segment, subtracts the payment, then continues the calculation for the remaining days.
How to Use This Calculator
- Enter the invoice amount, annual rate, and either dates or a manual overdue-day value.
- Set grace days, flat late fee, and any tax that applies only to interest charges.
- Select simple, daily compound, or monthly compound treatment based on your agreement.
- Add a partial payment and the day received if the customer paid after default.
- Submit the form to see the overdue amount above the inputs.
- Export the result as CSV for working papers or as PDF for notices.
FAQs
1. What does this calculator estimate?
It estimates overdue invoice interest, fees, tax on interest, and the final collectible balance using your dates, rates, compounding method, and payment timing.
2. Should I use simple or compound interest?
Use the method stated in the contract, purchase terms, or policy. Simple interest is common, while compounding is stronger and usually needs explicit authorization.
3. Why include grace days?
Grace days delay the start of interest. They help mirror customer terms where late charges begin only after an extra number of days.
4. What does the day-count basis change?
It changes the daily rate. A 360-day basis produces a slightly higher daily charge than a 365-day basis when the annual rate stays fixed.
5. How is the partial payment treated?
This version applies the payment against the overdue balance on the selected day, then recalculates the remaining period using the reduced balance.
6. Can I use this for legal notices?
It is useful for drafts and internal support. Verify contract language, statutory caps, notice wording, and tax treatment before issuing a formal demand.
7. Why might my accounting system differ?
Systems may round differently, capitalize charges at other intervals, or allocate payments to fees, tax, or principal in a different order.
8. Can I override the dates?
Yes. Enter a manual overdue-day figure when you already know the billable delay or when the source system has precomputed the delinquency period.