Could you tell me if there is any difference between the two compound nouns above ? For me, they are different to each other because my understanding is.
Payment is for purpose meaning some amount reserved for paying purpose while paid is for action meaning some amount taken (may or may not be different) from reserved amount is paid already.
Often there would be no difference.
If a difference were to be dictated by the context, then to me it would be:
last paid amount - the amount of money which was last paid into this account.
last payment amount - the amount of money which was last requested.
Example:
last payment amount due: XXXX
last paid amount: YYYY
Your account is in credit/deficit by: ZZZZ due to underpayment/overpayment.
As a newcomer I tentatively offer my understanding .
last paid amount = how much money has most recently been paid.
last payment amount = how much money has most recently been paid or how much money is needed for the last (concluding) payment.