What to know before mailing tax returns this year

How it works: Under the new system, a postmark is applied when the U.S. Postal Service processes the mail at a sorting facility, not when you send it.

• Under the old system, the postmark usually matched the drop-off date.
• Now, a return mailed on April 15 could be stamped April 16, which could expose some taxpayers to penalties or interest.

Threat level: The penalty is 5% of the unpaid tax — after subtracting any timely payments and eligible credits — for each month or partial month that the return is filed late, according to the IRS.

What's next: Taxpayers mailing returns should build in more time, per the latest guidance from H&R Block. Here's what to do before next week's filing deadline:

• Mail at least 3-5 business days beforehand (that means by April 10 at the latest).
• Ask for a manual postmark at the counter to ensure your return receives an immediate "round date" postmark even if it's sent on April 15.

Pro tip: Consider filing electronically instead or ask for a six-month extension.

• E-filing remains the safest option because it creates an immediate timestamp and avoids postmark delays.