WH invoice auto - when forgot WH code apply in prepayment

Guys

I am forgot to apply Witholding codes on prepayment which is 4.5% & made paymemnt for the same amount 200,000

after receiving actual invoice which is 250,000 so now enter the same std invoice & apply on prepayment which was 200,000 so the remaining amount will pay with pay in full function, but my question is how to create auto witholding invoice which is 200,000 x 4.5% = 9000 approx .

so in this above scenario, what is the best workaround for withholding invoice ????

kindly share some expert advice I am highly thankful to you ....

Faraz