TT figured my tax due plus interest. Received CP14 for some additional interest on estimated payments. Shouldn't TT program be able to do the tedious but simple math?

[DoninGA]

A CP14 is an IRS notice for unpaid taxes, not interest - https://www.irs.gov/individuals/understanding-your-cp14-notice

[lipp3692]

A rose by any other name...

[dmertz]

Unless you tell TurboTax not to, TurboTax does, by default, calculate the interest penalty based on the amounts and dates of your estimated tax payments and includes Form 2210 with your filed tax return.  However, your tax-payment entries may not agree with the details that the IRS has, or the IRS may find some income omitted from your tax return, so the result calculated by the IRS may be different.  The IRS then bills for or refunds the difference.

[lipp3692]

No 2210 in taxes, but many schedules were renumbered/combined last year.

[Anonymous]

you use a date that you will submit your payment.  the iRS uses the date received.    so if you date a payment.

if you want to avoid this issue in the future

1) use the irs website to make payments. you get credit on the date you specify even if the IRS doesn't take the money out for several days.

2) following 1) you don't risk delays in the mail or even the mail getting lost.