Why do I owe the IRS a penalty for underpayment on my wife's trust when I made all the estimated tax payments computed by TurboTax on time during the year?

[KrisD15]

Estimated taxes are just that, estimates. 

Did the income change from 2023 to 2024?

Are you sure you gave credit for the estimated tax payments on the return? 

[VerboseDaddy]

@KrisD15 Thanks for your response.  I did enter the estimated tax payments properly, so I did some more research after I posted the question, and I realized that there is no safe harbor for estimated tax payments for a business return, like there is with a personal return.  Since the trust's income was higher than the previous year's income, the estimated tax payments did not add up to 90% of the actual tax liability, so the penalty will still be assessed.  Under the rules for personal tax returns, there would have been no penalty, but that does not apply to a business return.