Voucher Prepayment

We currently use the 'Apply Vouchers to Prepayment' page to apply a regular voucher to a prepaid voucher.

We are trying to explore if this can be automatically done by voucher Post if we provide the same prepaid ref (in voucher attributes) on both the regular voucher and prepaid voucher.

However, I want to know if this automatic prepayment application feature has some limitations over manual application.