1. Wrong name or Social Security number

Every name and SSN has to match Social Security Administration records exactly. Newly married? If you haven't updated your SSA record, file under your old name for this year. A mismatch will get your return rejected on the spot.

2. Math errors and typos

The classic used to be adding wrong on paper. Now it's typing $50,00 instead of $5,000, or transposing two digits in a routing number. Tax software catches most of it, but always eyeball the numbers before filing.

3. Missing income

Forgetting a small W-2 from a summer job or a 1099 from a side gig is a common trigger for a CP2000 notice a year later — with penalties and interest. The IRS gets copies of everything. Match your return to your paperwork.

4. Choosing the wrong filing status

Single, Head of Household, Married Filing Jointly, Married Filing Separately, Qualifying Surviving Spouse — each has different brackets and credits. Head of Household in particular is often missed by single parents who qualify.

5. Missing signatures or forms

Paper filers still forget to sign. Both spouses have to sign a joint return. E-filers get their own version: skipping the identity-verification PIN or last year's AGI.

6. Bad direct deposit info

One wrong digit in your routing or account number can send your refund into someone else's account — and getting it back is painful. Double-check the numbers on an actual check, not a memory.

7. Missing the deadline

Tax Day is April 15 (or the next business day). If you can't finish, file Form 4868 for an automatic 6-month extension. But an extension to file is not an extension to pay — estimate what you owe and send it in by April 15 to avoid penalties.