The Salesforce Admin suggested the following solutions for the problems;

1) That an Approval Process will be created immediately a repayment record is created and receipt uploaded.

2) That a Finance Officer will be assigned a Repayment receipt once created who will then use a bank statement to verify transaction and if validated then the Finance officer can approve Receipt payment.

3) That the Rollup summary field “Total Actual Amount” should to updated using filters to only update customer balance once record status has been updated to ‘Verified”