S-Corp. Client made projected PTE payment via Form 3893 (WebPay) in December. We undershot by about a grand. I've reflected this correctly on Form 100S page 2 and the extra $1000 is showing up under tax due. I have verified it is NOT affecting underpayment penalties. My question is, is it okay to pay the remaining PTE with the return or must it be paid separately via Form 3893?