When creating a payment plan for a debtor, it's important to make sure every field has the correct information when selecting the calculation type.
Calculation Type: Simple calculation
If for Calculation Type the option Simple calculation is selected, the bottom field Instalment requires the amount of each instalment.
Calculation Type: Annuity calculation
If for Calculation Type the option Annuity calculation is selected, the bottom field Number of terms requires the total number of instalments.