I am currently working on a payment form. It's absolutely required that our users are allowed to edit the amount they want to pay.
Currently, the way I am handling this is to have an editable 'amount to pay' field. It will be prefilled with their current balance.
If a user edit this amount, what is the best way to warn them that they might be overpaying or underpaying their balance?
Main options I've considered:
- Do nothing, and let them continue. If they edited the amount, they are aware.
- Throw a modal that confirms they want to pay a different amount than balance owed
If users overpay:
- Their payment will be applied to this balance, other balances they might have, or refunded. We can't know straight away if they have other balances.
If users underpay:
- As long as they are before their due date, they are fine. If they underpay, then still have a balance by due date, they get a fee - same as if they just didn't pay.