Should I mail another check in case there was an error on the first one?

[MichaelMc]

No. If there is a problem with your tax payment, the IRS will send you a bill and provide an opportunity for you to correct the payment in a timely manner. Are you simply concerned because your check has not yet cleared the bank? At this time of year, the IRS is processing millions of tax returns daily; it takes a bit of time for everything to be processed.

If you were to mail in a second check, the most likely scenario would be that both payments would be processed and you would wait several months to get your overpayment refunded.