How to Refuse Mail

Refusing and sending back unwanted mail delivered to you by the USPS is a very simple process:

Write “Refused” on the mailpiece. I’d suggest doing this near the postage area, although that can be hard to find on some pieces of junk mail. I tend to use a black marker for it to make sure it shows up, but I’ve used a normal pen and it works just as well. Or if you do this a lot, you can even have a rubber stamp made up (they’re not very expensive) and use that.
(Optionally) Make a few dark marks through the barcode and address. This isn’t always needed, but it can help make sure that the automated sorting equipment doesn’t just redirect the mailpiece right back to your mailbox without anybody looking at it. You don’t need to obliterate the address or barcode, you just need to do enough that it won’t be read automatically.
Give it back to the US Postal Service. Essentially, put it wherever you put the rest of your outgoing mail. I just put it back in my mailbox and raise the flag. If you prefer, you can stick it in a regular blue collection box, or even go into a Post Office and hand it to a clerk there. The mail just needs to get injected back into the mailstream somehow.

Caveats to be aware of

While refusing mail is very easy, there are some details that you need to be sure to be aware of.

You can only refuse unopened mail. If you open the mail to see what’s inside, you need to throw it out or recycle it yourself, since the Postal Service won’t take it. By opening it, you accepted the mailpiece. See the next page on determining junk mail if you want some tips for figuring out what’s junk mail and what isn’t before you open it.
Mail that is sent to you as registered, insured, certified, or collect on delivery (COD) generally required your mail carrier to physically give you (or somebody at your address) the mail. If it isn’t refused right then, you give up your right to refuse it. Luckily, this isn’t generally an issue since mail sent that way is usually actually important and not junk mail.
If you send somebody a sales promotion, solicitation, announcement, or other advertisement, and they respond to it, you also need to refuse it immediately when offered for delivery, and not afterward. Again, this generally isn’t the case when talking about junk mail.

Postal Service regulations

This page is just a summary of my understanding of the rules one needs to follow. If you’d like to read the instructions directly from the United States Postal Service, refer to these pages: