Monthly periods simplify a changing balance
DebtZero models interest and repayments monthly with a fixed annual rate. Real agreements may calculate interest daily, use different rules for purchases and cash advances, or change rates during the plan. CFPB explains that many credit-card issuers calculate interest using daily balances.
New spending, fees, payment timing and rounding can also change the result. The app does not automatically import these events. A date shown by the forecast is therefore conditional on the information and assumptions you entered.
Use the rate the model actually needs
Check what a quoted annual percentage represents in your country and agreement. A total-cost measure that includes fees is not necessarily interchangeable with the interest rate applied to an outstanding balance. DebtZero does not derive a complete contract model from a country setting.
Check minimum-payment settings separately. A simplified percentage or fixed amount can differ from a lender’s floor, interest-plus-fee rule or changing requirement. Use the provider’s terms when deciding what must actually be paid.
Keep estimates useful by updating facts
When a new statement arrives, use check-in to update the saved balance. Review the rate and terms if they changed. Payment records alone do not reduce DebtZero’s stored balances.
Compare scenarios to understand direction: what changes if the budget is higher or an extra payment is possible? Avoid interpreting a small forecast difference as a guaranteed saving. If the agreement is complex, obtain an explanation from the provider or an appropriate local adviser.
Sources and further reading
Sources checked on 24 September 2026.
An educational planning tool, not personalised financial, legal or debt advice. Estimates use your inputs and simplified monthly assumptions. Your lender’s statements and agreement remain the reference.