Mistake of 12.5%vat instead of 4% vat

create debit note, party will adjust itself ,i think its there responsibility.

If your sold to party is not end customer of that material then they may take Input credit of full VAT charged by you so it may not be a problem for them. if they are end customer then you must reimburse them the difference amount & same way you can also raise debit note to your vendor party for the difference amount.

I guess I am right.........