SAN DIEGO (CBS 8) - Ready or not, Wednesday was the last day to file your taxes, or ask for an extension, but even with an extension, individuals still have to pay what they owe.

Some San Diegans smiled as they mailed off their taxes on by the deadline day. If you have not filed, San Diego State University accounting professor Nathan Oestich said it's okay.

Professor Oestich said he is one of more than ten million Americans who filled an extension, however, an extension must be filed by midnight on Wednesday.

An extension will delay having to file taxes until October, but if money is owed, it still has to be paid by the midnight deadline.

"If you do not submit the entire amount, you're dealing with penalties and interest," he said.

Since the Midway Post Office was closed for restructuring, last minute filers can go to the Carmel Mountain Ranch area post office. Workers will be available to take taxes from individuals and give a Wednesday postmark.

If you race through your taxes and realize you made a mistake, do not file another return. In most cases, you have up to three years to amend your taxes. If you owe money, you will have to pay interest and possibly some penalties.

The Carmel Mountain Ranch Post office expects a steady stream of cars right up to midnight, but 88-percent of those filing taxes, will do it electronically.