Help: Interest Calculation
A complete debt-with-interest analysis tool — supports multiple principal amounts, expenses and payments on different dates, with automatic interest calculation per rate period. The form is divided into tabs.
Debt Amounts
Other Expenses
Payments
Client Interest Rates
Parameters
Analysis
Result
| Date | Amount | Description |
|---|---|---|
| 01/01/2025 | 5.000,00 | Initial principal |
The form tabs
- Debt Amounts
- Enter the initial principal amount(s) here — you can add as many rows as you like ("New Entry"), e.g. if the debt was created in installments/parts on different dates.
- Other Expenses
- Additional expenses (e.g. legal costs, third-party default interest) beyond the main principal. The "Bears interest" checkbox determines whether that specific expense also generates interest or remains interest-free.
- Payments
- Amounts already paid against the debt, with their date — the application deducts them correctly in order of priority (interest first, then expenses, then principal).
- Client Interest Rates
- Active only when you select Interest Rate Type = "Client" in "Parameters". Here you enter your own/agreed interest rates per period, instead of using the official ones (Default/Contractual). A table with the current official rates is also shown alongside, for comparison.
- Parameters
-
- Interest-bearing days per year: 360 or 365 — the basis for calculating daily interest.
- 366 days for a leap year: if active, leap years are calculated with 366 instead of the selected base.
- Interest Rate Type: Default interest (the highest, for overdue debts), Contractual (the agreed rate), or Client (your own rates from the "Client Interest Rates" tab).
- Semi-annual compounding: if active, the interest of each half-year is added to the principal and also earns interest in the next half-year (compounding).
- Analysis / Result
- These appear after the calculation. The "Analysis" shows each sub-period in detail (depending on interest rate changes) with days, rate and interest. The "Result" shows the summary picture: principal/expense debt, total interest, total payments, and the final remaining debt.
The buttons in the top right
- Recalculate: reruns the calculation with the current data.
- Clear: empties all tabs (principal, expenses, payments, interest rates), with a confirmation prompt.
- Save / Load: you can save the entire case (all data and parameters) to a .json file on your computer, and reload it later to continue — useful for keeping a separate file per case/client.
- Excel: downloads the full analysis as an Excel file.
Frequently asked questions
The contractual rate applies to agreed debts within the deadline, while the default interest rate (higher) is imposed when payment is delayed beyond the agreed date.
No — only "Debt Amounts" is required. The others (Other Expenses, Payments, Client Interest Rates) are filled in only if they apply to your case.
JSON keeps all the input data (principal, expenses, payments, parameters) so you can reload it and continue later or correct it. Excel is for the final result/analysis, not for editing within the application.