Non-Machinable Letter: Meaning, Shipping Process & Cost

Sending letters has been a popular way of communication for centuries. The USPS alone oversees the processing of billions of mail items annually. During processing, a letter gets classified as either machinable or non-machinable. 

Machinable letters are mail that can be processed directly by USPS’s automated machines. On the other hand, mail pieces that cannot be processed directly are regarded as non-machinable. 

To better understand this concept, this guide explains what a non-machinable letter is, how mail processing works, and the USPS standards for machinable letters. You will also learn how USPS handles non-machinable letters and how much it costs to ship them. 

What is a Non-Machinable Letter? 


A non-machinable letter is a mail piece that cannot be processed by USPS automated machines. Typically, these are letters with unusual shapes or non-standard sizes. 

They undergo manual handling and sorting since they cannot be processed efficiently or directly via the automated machine. This process is time-consuming and more expensive. 

Understanding Mail Processing

Before delving into what makes a mail or letter non-machinable, it is crucial to understand how USPS mails are processed: 

  1. USPS collects mail from mailboxes, businesses, drop boxes, and other post offices. 
  2. After collection, this mail undergoes “culling”. This process separates machinable letters from those that are not. 
  3. Mail categories are transported to a processing facility via trucks, planes, or trains.
  4. Processing involves sending machinable letters through high-speed automated machines, which can sort up to 36,000 mail pieces per hour. On the other hand, non-machinable letters are sorted manually. 
  5. Sorted mail pieces eventually get transported to individual post offices for delivery to the recipient. 

USPS Criteria for a Machinable Letter

  1. A machinable letter should have a length not greater than 11.5 inches or a height above 6.125.
  2. The ideal weight for a machinable letter is anything below or at 3.5 ounces. Anything above is non-machinable. 
  3. A machinable letter should have an aspect ratio (length divided by height) between 1.3 to 2.5, with a thickness of not more than 0.25 inches. 
  4. A machinable letter must have a uniform thickness and contain no rigid items such as pens, jewelry, keys, or discs that can get dislodged. 
  5. The letter’s address must be in the right spot (upper-left corner) or be non-machinable. 

Can You Ship a Non-Machinable Letter? 

You can ship a non-machinable letter, but it has to be done manually and will cost you a few extra bucks. USPS charges an additional non-machinable surcharge of $0.25 per piece on top of the standard First-Class mail rate. 

This is currently at $0.55 for letters weighing up to 1 ounce. Here is what you need to ship a non-machinable letter: 

  1. Enclose the letter in a sturdy or rigid envelope. This protects the letter’s content from being damaged during manual handling. 
  2. Properly address the letter. It is best to print such an address or legibly write them.
  3. Pay the postage fee for using stamps, online postage, or metered mail. 

Other Key Takeaways 

  1. You can use a Forever stamp instead of a non-machinable stamp. However, it means you will be paying more. 
  2. USPS also imposes a non-machinable surcharge fee for postcards. The fee is currently $0.20 per postcard. 
  3. A non-machinable flat mail shares the same criteria as a non-machinable letter. 


Do non-machinable stamps expire?

Non-machinable stamps do not expire. The stamp will always remain valid for the printed rate, just like a Forever stamp.

Can you send a letter without a stamp?

No, such a letter will be returned to the sender for postage.

What happens if you put the wrong stamp on a letter?

It will be returned to you for additional postage. Your letter will not be shipped until it has the correct postage amount. 


Non-machinable letters are mail pieces that cannot be processed efficiently by the USPS automated machines. Therefore, they require manual handling and sorting, which usually attracts extra surcharges and is time-consuming. 

If you wish to avoid this, it is essential to understand and obey the USPS criteria for machinable letters. On the other hand, if you insist on shipping a non-machinable, ensure the letter is in a sturdy envelope with the right address printed on it. 

You can then pay the postage for the stamp and ship the letter without any issues. 

I hope you found this guide helpful. Feel free to explore Threaller for other USPS-related guides. 

Thanks for reading.