Every year, many taxpayers may make mistakes on their returns that cause IRS processing delays. Some common errors may also result in paying too much or too little tax. A miscalculation in either direction can be costly, since the IRS may assess penalties for underpayment.

The following mistakes may not change your tax, but they can cause processing problems. The IRS may even withhold your refund until the errors are corrected. Be sure to check for the following:

Missing or Inaccurate Social Security Number (SSN): Even when filing electronically, many people mistype their SSNs and do not catch the error. If the SSN on your return does not match the number on your Social Security card, the IRS may not be able to process your return.

Misspelled Name: Take your time when filling in every blank on your return, even your name. A misspelling or illegible writing can prevent proper processing.

Incorrect Bank Account or Routing Number: Getting your return filed electronically and requesting direct deposit is the fastest way to get your refund, IF you provide accurate information. An error in your banking info can cause big headaches.

Missing Signature: Remember that in most cases, couples filing jointly must both sign their return.

Math Mistakes: Even mathematicians sometimes make errors in simple addition and subtraction, and some of the calculations required for 1040 schedules can be complicated. Thoroughly double-check every bit of math on your return.

Incorrect Filing Status (Single, Married Filing Jointly, etc.): The IRS will not accept a return showing a filing status that you are not eligible to claim. If you qualify for more than one status (for example, filing jointly or separately if you are married), the option you choose may significantly change your tax.

Incorrectly Figuring Credits or Deductions: Once you determine that you qualify for a tax deduction or credit, you must carefully compute the amount that you can claim. Many taxpayers fail to take into account income limitations (including the calculations that must be made if your income falls within a “phase-out” range) and other restrictions. Others claim less than they could, or miss out on deductions and credits entirely by not filing the required forms and schedules.

Expired ITIN: Those who file their IRS returns using individual tax identification numbers (ITINs) must keep in mind that ITINs periodically expire. Although a return filed with an expired ITIN may be accepted, the IRS generally will not allow any of the exemptions or tax credits claimed. The taxpayer must renew their ITIN in order to obtain the full refund that they are owed.

To avoid costly mistakes, a tax professional can help prepare or check your return and file it electronically. A tax pro might also help you claim deductions and credits that you would otherwise miss.