Local post offices will not extend hours on tax day, Monday, April 18, the United States Postal Service in Indianapolis said.

“In Indiana, post offices will maintain their regularly scheduled operating hours on April 18,” USPS said in a statement released on Monday. “To ensure cancellation on April 18, postal customers must deposit tax returns at post offices prior to scheduled closing times or mail returns in local blue mailboxes prior to scheduled pickup times.”

Mailers can go on line at usps.com—click on “Locate a Post Office”—to verify operating hours of post offices for April 18 and to locate alternate sites to purchase stamps and conduct postal business.

Other tips:

•Mail tax returns in local mailboxes. “This helps avoid the mad rush to the post office,” USPS said. “But keep in mind that corner collection boxes have final pickup times—customers must ensure they mail prior to the final pickup times posted on the mailbox.”

•Use first-class postage. “The Internal Revenue Service recognizes the inexpensive first-class letter postmarks as proof that a return has been mailed on time,” USPS said.

•Write clearly. “Handwritten tax return envelopes must be legible,” USPS said. “And don’t forget to seal the envelope and include your return address.”

•Double check postage. “New prices for mailing letters, cards, oversized envelopes, and packages will take effect on Sunday, April 17,” USPS said. “Although the cost to mail a one-ounce first class letter is still 44 cents, the cost of an additional ounce will increase from 17 cents to 20 cents.”

•Envelopes exceeding 6 1/8’’ x 11 1/2’’ or more than 1/4’’ thick will require additional postage. Please consult usps.com—click on “Calculate Postage,” top left—or visit your local post office to determine correct postage.

•“Tax agencies do not accept postage due mail and tax returns bearing insufficient postage will be returned—meaning taxpayers will be penalized for filing late tax returns,” USPS said.

“We recommend mailing your return as early in the day as possible to avoid that last-minute dash to the post office,” USPS spokesperson Kim Yates said. “Just deposit your tax return at your local post office or in a blue collection box before the last scheduled pickup time. As long as you do, your tax return will be postmarked April 18, 2011.”