By now, you’re definitely aware that today is Tax Day, but what time is the deadline to pay Uncle Sam?

It depends how you choose to file, and whether you have to pay.

Penalties for missing the April 15 deadline are only incurred for those who owe taxes to the Internal Revenue Service (IRS). However, if you’re one of the 75 percent of people getting money back, there’s no need to scramble.

"If you're expecting a refund, don't panic," Stanley Veliotis, associate professor at the Fordham University School of Business, told USA Today. "The sooner you file the better so you can get your money back, but it's not like you have to file on April 15. If you have a refund coming there's actually no penalty for filing after April 15."

However, if you owe taxes to the IRS, it is strongly recommended to file by the end of April 15 to avoid paying penalties. If you file late and fail to pay on time, you will incur a maximum penalty of 5 percent for each month following the deadline. If you wait longer than 60 days, you’ll incur a $135 fee, or 100 percent of the unpaid tax.

If you’re a procrastinator, you can also join the 12 million taxpayers who have requested extensions for filing their taxes. The six-month extension, with an Oct. 15 deadline, can be requested using IRS Form 4868, but you’ll still have to pay 90 percent of the tax you owe by the deadline Tuesday.

But if you plan to make Tuesday your target, the deadline time varies.

If you choose to file online through the IRS website, given your adjusted gross income was $58,000 or less in 2013, you have until midnight to file electronically.

Internal Revenue Service Commissioner John Koskinen said 85 percent of tax returns are filed electronically, rather than via mail.

"I remember you just didn't want to be at the post office on the 14th or 15th," Koskinen, who became head of the IRS in December, told USA Today. "Now, whenever you're ready to file, you just file."

The 74-year-old said he is joining the majority of Americans and utilizing electronic filing for the first time ever year this.

If you’re using snail mail to file, your forms must be postmarked today. To ensure getting the April 15 postmark, deposit returns before the last scheduled pick-up time. Check your local post office to verify final collection times or check the pick-up schedule on collection boxes. You can also get additional security using certified mail service, with proof of mailing, proof of delivery and a return receipt.

The United States Postal Service is also offering extended hours on April 15 at some post office locations. Check the website to see which locations are open past business hours.

However, not all cities are catering to procrastinators filing taxes late. Cities like Sacramento, Calif., have virtually opted out of extended hours, since the demand is just no longer there.

"It was very festive," Sue Brennan, spokesperson for the United States Postal Service, said of the days before Internet became more prevalent. "April 15 used to be a major postal event across the country. At least in the last 10 years for sure, it's all but gone away."

In Boston, Mass., one post office, the Boston Fort Point Post Office will be open until midnight along with the James A. Farley post office in New York City.

While you’re at it, be sure to check out some of the freebies you can score on April 15 offered by businesses in honor of Tax Day.