Can I Use Package Services to Send Flats with USPS?

Flats need to be mailed with the United States Postal Service, and not shipped
ship flats with USPS
Written on:

A lot of people ask us whether or not they can ship flats with USPS. Technically, the answer is no. While you can send flats with the Postal Service through the mail, you can’t use any of USPS’ shipping services such as First Class Package Service. Sorry!

What Does USPS Classify as Flats?

“Flats” refer to large envelopes, newsletters, and magazines. In fact, USPS uses the phrases “large envelopes” and “flats” interchangeably to describe the same thing. A good example to think of are those manila folders that you see in the above photo.

According to USPS’ website, flats must:

  • Have at least one dimension greater than 6.125 inches high, 11.5 inches long, or 0.25 inches thick
  • Have maximum dimensions no more than 12 inches high, 15 inches long, and 0.75 inches thick

Here’s what it all comes down to. If you want to use First Class Package Service instead of First Class Mail Flats, your package needs to be rigid, lumpy, and/or most importantly, thicker than 0.25 inches.

Pro Tip: Don’t confuse flats with Priority Mail Flat Rate boxes or envelopes! They are two entirely different things, and require different types of postage.

Large Envelopes Technically Need to Be Mailed, Not Shipped

Since USPS clumps flats and large envelopes into their regular mail stream, flats don’t come with tracking numbers automatically. If you’re sending sensitive documents and would like to be able to track them, we suggest purchasing Certified Mail service for your flats. Certified Mail is a mail service a tier above First-Class Mail that assigns a tracking number to your envelope.

Keep in mind that if you purchase a shipping service such as First Class Package for an envelope that looks like a flat, USPS may return it back to you. You’re better off just sticking with regular First Class Mail or Certified Mail.

Learn more about the difference between mailing and shipping.

Last Updated:
Share on Facebook Share on Twitter Share on Reddit Share via Email


Post a Comment
  1. p youngling

    I was sending a magazine 2 weeks ago and the price was soooo much more then – -that it was today AND I dealt with the same Clerk ..But today I had a new clerk who was there to help me !!! And the price was really different YES I knew there was a problem with him….(He does NOT know his job !!! and I suffered for it (NEVER AGAIN) –The clerk I had today was very nice and very helpful (CLERK – 05 ) Someone needs to talk and see if the other clerk NEEDS HELP as far as HIS job is. (don’t know HIS name or number – – BUT , He is the only male in the EDGEWATER office Zip code 21037 . Thank You for the time, Please help …

    • Cindy Furcean

      I totally agree with this comment from P Youngly. I worked for a very large Marketing company and handled all our National Clients mail. At the time bulk mailing was new. I did everything that was right with the mailing with thousands of pieces of mail. It was so frustrating because the Post Office doesn’t give their employees any up to date changes with regulations or prices, and when I dropped off most mailings, they had no idea how I how I got lower rates than they did. It seemed all the Postal Conferences I attended was the only way I could keep up with Postal rates with their discounts. The Post Office offers (they did back then) postal rate books and charts, but if I had to drop off any mailing the employees really hadn’t a clue how to handle it. Its the Post Offices fault not educating their employees. Be kind to the worker who didn’t give you a lower rate. Its Upper Management that should be aware of the lack of knowledge they have in their Post Offices.


Post a Comment

Your email address will not be published. Required fields are marked *


This site uses Akismet to reduce spam. Learn how your comment data is processed.

Related Shipping Guides