The IRS estimates that nearly 5 million people have not filed their taxes, but all returns must be postmarked by midnight on April 18. Filers that need more time can request an extension.
The deadline was delayed three days because of Emancipation Day, which is a legal holiday in Washington D.C.
Officials said waiting to the last minute can put many people at risk for scams and identity theft.
Some counties in Pine Belt have been granted an extension because of severe weather. Those counties include Forrest, Jones, Marion, Perry and Wayne.
Residents that live in counties affected by flooding have until July 15 to file their returns and pay any taxes due.