Tax Day, which falls on Tuesday, April 18, is the deadline for filing taxes on income earned in 2016. Usually, April 15 is the day taxes are due, but in 2017, that falls on a Saturday. And on Monday, the District of Columbia celebrates Emancipation Day, which is normally April 16, but that’s a Sunday.

Emancipation Day affects taxes the same way federal holidays do. Therefore, the tax deadline is pushed out to the following Tuesday, April 18, giving taxpayers three extra days to file their returns.

Postal customers are encouraged to visit usps.com for post office hours. Many post offices regularly are open after 5 p.m. Due to heightened security, mail that bears only postage stamps and weighs more than 13 ounces must be taken by the customer to a post office retail counter.

Tips to remember:

• Mail early in the day at any post office. Be sure to verify post office hours of operation;

• If depositing a tax return in a collection box on April 18, double check the pick-up time on the collection box. Your tax envelope must be deposited prior to the last scheduled pick-up time posted to receive the April 18 postmark;

• Affix the correct postage. Some tax returns include many forms and require additional postage. For first-class letter-sized envelopes, one ounce is 49 cents and 21 cents for each additional ounce. A two-ounce letter-sized envelope is 70 cents. For a first-class flat-sized (8.5 inch-by-11 inch) envelope, the cost is 98 cents up to the first ounce and $1.19 for up to two ounces; and

• Customers may purchase postage at the retail counter or at a self-service ship and mail center (credit/debit card only) in the post office lobby. Stamps also are available at alternate retail access locations posted at usps.com.