Dear Farheen,
That's not possible in a normal sales invoice, because it doesn't feature prepayments.
What I would advise is the following:
Create a sales order (instead of a sales invoice) and within the sales order enter the % that needs to be prepaid.
After processing the prepayment the remaining invoice is split into two parts: the amount that needs to be paid and the amount that already has been paid. Seems to me, also from a financial perspective the best way to process invoices that are paid into multiple parts.
Kind regards,
Floris
