Solution
1. In the Customer Payment page, when Auto Apply = True, the payment will be applied based on the order of the Invoices in the list under the Apply tab > Invoices subtab.
2. It does not necessarily mean that it will apply to the latest Invoices/Transactions.
3. In order for the Payment to apply on the oldest Invoice, sort the Date column by clicking on the Date Column Header such that the oldest Invoice will appear at the top.
4. This is a sticky feature which means that whatever is the sorting from your last Payment transaction will be the default in your next Payment transaction.
In case, it applies the Customer Payments to newest Invoices instead of the oldest:
1. Navigate to Transactions > Customers > Accept Customer Payments
2. In the Payment page, enter any Customer with multiple open Invoices/Transactions.
3. In the Apply tab > Invoices subtab, click the Date Column Header to sort it from Oldest to Newest
4. Navigate to Transactions > Customers > Accept Customer Payments again
5. Enter the same Customer and verify if the Invoices/Transactions are now listed from Oldest to Newest as default
6. Try importing your CSV file for the Payments again
Expected Results: Customer Payments imported via CSV to will be automatically applied to oldest Invoices first