iStock/ThinkstockMore people are e-filing their income taxes but some still want to do it old school and use paper forms.

“When you do a return on paper, the opportunity to make mistakes really mushrooms,” says IRS spokesman Eric Smith.

If you opt to file your taxes the old-fashioned way, Smith says you should make sure you “check your math on the return, that you attach all required documents, such as the W-2, your supplemental schedules if you’re itemizing deductions.”

“If you send in a return and it’s incomplete, we’ll just have to send it back or request the supplemental documents,” he adds.

Anthony Burke with the IRS suggests trying the agency’s free fillable forms.

“Anyone can use it,” Burke says. “There’s no income limitation, as there are on the other programs for free file.”

“You’re presented something that looks like an electronic 1040. You work through the form, just like you would through a normal form. It does do some math, and as soon as you’re done, you e-file it,” he explains.

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