New Law Helps Taxpayers Fight Claimed Mistakes on Tax Returns

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For most of us, the only time we want to see an envelope from the IRS is if it contains a tax refund check. So when we see an envelope from the federal tax agency that doesn’t contain money, we get nervous.

Wondering what we did wrong, we tear open the envelope. We pull out a short, cryptic letter that says the IRS had discovered a math error on our return. The letter states that the IRS has corrected the mistake, increasing our tax liability.

That might be a relief if the amount of money involved is nominal, but what if we think the IRS is wrong? How do we fight them? The letter contains no contact information. And nothing in the letter says whether there’s a deadline for us to protest.

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Well, new bipartisan legislation, recently signed into law by President Donald Trump, known as "The Math Act," is set to change the dreaded “math error” IRS notification system.

The changes, which will become effective in late 2026, are supposed to help taxpayers better understand their often minor tax return errors and, importantly, their taxpayer rights when dealing with the IRS.

Here’s more of what you need to know.

IRS math error notices sent to millions each year

Millions of people receive “math error” notices from the IRS every year. These notices are meant to handle simple errors that result in a tax deficiency more easily and streamlined than through more formal means, like a notice of deficiency.

The shortcut, however, is only meant for obvious mistakes, like miscalculations, missing required return schedules, or mismatched entries between forms.

The problem is that these notices are often vague and confusing. They often do a poor job of telling taxpayers the IRS’s exact reasons for the adjustments to their returns.

Sometimes the notice might list several possible sources of error rather than specifying the exact issue.
Not only that, the letters often fail to tell taxpayers that, by law, they have 60 days to protest an adjustment with the agency before it becomes final.

So, a taxpayer who might want to file an objection may never get the chance.

"For too long, the IRS has caused headaches and confusion when a taxpayer makes a fixable mistake on their taxes, providing no explanation as to why a refund is different than expected, or how to correct an error," said Rep. Randy Feenstra (R-Iowa) in a release about the new legislation.

IRS Math Act to the rescue: Key provisions

Enter the Math Act. In early December, President Trump signed the IRS Math and Taxpayer Help Act, requiring the IRS, in cases of mathematical errors, to provide detailed information notices when the error correction results in increased tax liability.

Specifically, the new law says the IRS must:

Describe the error in plain language, including the type of error, the applicable Internal Revenue Code section, and the specific line of the tax return where the error occurs
Show a detailed computation of how the IRS’s proposed adjustment affects the applicable return section
Include the IRS automated hotline for requesting account transcripts
Display the 60-day abatement date in bold font on top of the front page of the notice
Stop reporting multiple alternative errors instead of adequately describing the error underlying the adjustment

How the Math Act could help taxpayers

Many lawmakers and industry professionals on both sides of the political aisle believe the new law will help taxpayers.

On its website, the National Taxpayer Advocate office applauded the legislation as "a long-overdue reform that strengthens taxpayer rights, improves transparency, and ensures fairness in IRS communications."

Plain language math error notices tied to returns means taxpayers will no longer have to interpret vague or technical letters, which should help reduce confusion and anxiety. The new legislation is expected to:

Improve the efficient resolution of IRS taxpayer disputes. Specificity in the information flagged allows taxpayers to respond to notices in a timely and accurate way.
Enable taxpayers to provide the correct documentation the first time, reducing IRS work volume
Provide taxpayers with a clear understanding of their rights and the steps they must take to challenge an IRS adjustment within the 60-day deadline
Strengthen public trust in tax administration and promote voluntary compliance

Note: The Math Act likely won’t be fully implemented until late 2026. The IRS says it needs time to develop a formal process for taxpayers to potentially challenge math error notices.

In the meantime, with tax season just around the corner, try to avoid other common tax return mistakes like forgetting or mistyping your Social Security Number on your return, using an incorrect filing status, or failing to sign your return before you file.

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Roxanne Bland, a self-styled “tax nerd,” has worked in the tax field for over 30 years as a state tax legal analyst. Before joining Kiplinger as a tax writer to help ordinary people make sense of their federal and state tax obligations, Roxanne spent many years covering developments in state tax jurisprudence at the U.S. Supreme Court and worked closely with state revenue agencies to develop uniform tax legislation. She has also contributed to Tax Notes State, a Tax Analysts publication focusing on cutting-edge corporate tax issues.