Why Does the Post Office Deliver Mail That Has No Stamp?

If you had asked me that question a week ago, I would have said with great certainty that the post office would not mail a letter without a stamp.

A few days ago, however, my daughter got a letter delivered in the mail. Where the stamp should have been, the sender had instead written, “Exempt from postage: Guinness Book of World Records attempt.”

The envelope contained a single sheet of paper, describing an attempt to set the record for the world’s longest running chain letter, along with instructions to pass this letter along to seven friends. If we broke the chain, the Postal Service (which is monitoring the record attempt) would know that we were the individuals who ruined it for all of the people who had been part of the chain since 1991!

The simple arithmetic of chain letters guaranteed that somebody was lying.

A chain letter for which every recipient actually forwarded the letter to seven other people would quickly absorb every child in the world (7 raised to the power of 10 is roughly the U.S. population.) I did, however, give the sender credit for at least admitting this was a chain letter.

The thing that puzzled me was why the Postal Service was aiding and abetting this effort. It seemed bizarre, but at the same time lent credence to the endeavor. Maybe this really did have something to do with a world record bid.

A quick Google search, however, revealed that the Postal Service isn’t condoning the chain mail. Actually, the explanation for why the letter got delivered without postage is even more interesting to me: apparently the automated mail sorting machines fail to catch many letters that are missing a stamp.

On reflection, this does make sense — profit maximization requires setting the marginal cost of an action equal to the marginal benefit. If almost all letters have stamps, then the benefit of checking each one with 100 percent accuracy is infinitesimal, so it makes sense to let some unstamped letters through. (The same idea holds for catching people who don’t pay their train fare.)

Now I am curious to know exactly how lax the Postal Service is. Perhaps some blog readers with plenty of extra time on their hands can experiment with this by sending a bunch of unstamped letters and see how many make it to the destination? We will report the results here on the blog if someone rises to the challenge.

I’m just about to drop something in the mail. Maybe I’ll skip the stamp — though I suspect my tax return will make its way to the I.R.S., stamp or no stamp.


you want to send a letter without postage?
address it to yourself with the return address to who you really want it to go to.
Then USPS will "return" it for lack of postage.
Or you'll get it back the next day to try again.

Either that or just send an email.


RE: #2

I would love to see FedEx even try delivering letters for $0.41. NOT GOING TO HAPPEN.


Steve, you wonder how lax the Post Office is?

You do realize that it is ran by the most inefficient organization in the United States (the government), right?

Let Fed Ex take over the Post Office and I GUARANTEE you that they could reduce the stamp rate 20%, not raise any other prices, and STILL MAKE A PROFIT!

Quite simply, without the incentive to make a profit, and WITH the government-mandated monopoly on letters that the Post Office has, the incentives are all in the direction of inefficiency. They don't have to be hungry.

Make a couple of simple changes and things will be very different: Take away the monopoly and allow the post office to make a profit. And just as Fed Ex forced the Post Office to compete in overnight delivery, etc., so, too, will the competition for sending letters suddenly force efficiency into the organization.

The price competition will force even greater efficiencies.

But wait, that will never happen--we ARE talking about the most inefficient, moribund organization in America. We must not forget that they DO NOT CARE about efficiency.



I'm pretty sure that here in the UK they just charge the recipient. The postman simply fines the person to whom the unstamped letter has been sent - otherwise he will not hand over the letter.

Whether the marginal cost of recouping this money (which is measured principally as the deliverer's lost time) is greater than just delivering it, I have no idea.


You HAVE to check out Improbable Research.They've done testing on the US mail system to show that you can mail ANYTHING and what happens when you try to, say, mail a brick without any packaging. It's a hilarious article.



Putting a stamp on your letter works on the honour system. Always has. There's nothing new about this. It's not so much a specific decision to take this approach as a lack of incentive to change.


Pure altruism? ;-)


i'll be trying this in singapore. i'll let you know. :)


A number of years ago I worked in a mailing operation at a savings & loan. We sent out between 250k and 400k pieces of mail per month. Even with our automated equipment the occasional piece of mail went out without postage; I know that some ended up being delivered, although we always got a small number that USPS returned for postage. I could count on one hand the number that arrived at the customer with "postage due" (and I know that 'cause said customer invariably complained loudly about it).

On at least one occasion in 1993 we sent out c. 1,000 pieces, all at once, without any postage. About 200 were returned. As far as we could tell the rest were delivered. Of that batch, oddly enough, we received not one complaint about "postage due." What makes this particular event remarkable is that the entire block of unmetered mail made up the contents of two letter-trays; they were all together. So why did the USPS choose to send some along, but not others? It would have been much easier on the letters' handlers to scoop them all up, together, and return them in one block, just as they had been delivered ... so I can't attribute it to laziness.

Go figure.



Don't encourage free-loaders. Like your donuts case, it's also largely a case of goodwill. It is inevitable that people who send plenty of letters will occasionally forget to stamp one. It is human nature that the lost/undelivered letter is the one that everyone remembers as the anecdote.

The post office loses enough letters anyway, the marginal cost in lost goodwill of failure to deliver is likely to be far more than the marginal cost of delivery, so long as the proportion unaddressed is very small. If a significant of your letters fail to arrive then you'll stop using their service.

It's the same reason any "sensible" shop owner will always let you off a missing penny etc. This only works so long as excessive people don't take advantage of it, which is why I think the comparison with trains is an inaccurate one.

Mark B

Are you using your blog to call for theft of service? I'm not against it, I was just curious.


While I am not a huge fan of the USPO, it does seem like it is critiqued somewhat unfairly. If FedEx were required to ship most anything and everything that showed up at it's stores, rather than using their few envelope/box choices, I doubt they would be as efficient as they are now. Like Amtrak, the Post Office is hamstrung by requirements placed on it by the government, but then they are also expected to be efficient.

Back to the original post, I have occasionally received mail without postage or with insufficient postage (which is more frequent). I always assumed there was some sort of spot-checking system in place to encourage people to post correctly.


For all of the complaining that is done here about the USPS, I still find it utterly amazing that you can have a letter shipped anywhere in the US...generally within a few days...by writing just 2-3 lines of coordinates (i.e., someone's address) on it...for just $0.41! If the USPS (and other shipping companies) did not exist, imagine the logistics and cost of trying to have letter delivered from NY to LA, or to Hawaii for that matter!


I've sent a package to my parents with the incorrect postage. They had to go to the post office and pay off the remaining amount before being given the package.


franky, i'm willing to pay a few cents more for a stamp so that the usps provides as good a service as it does. why? not all tasks and businesses work properly under privatized, non-monopolistic open competition. it may lower costs, but you get what you pay for, and it *WILL* lower quality.

Mark Nelson

Yes, USPS is fallible and makes mistakes. However, I'm continually amazed that they are able to do what they do for the prices they charge. No way any private company would take on the job they do given the constraints.

For example, I mailed two 27 pound boxes of books to the Texas Department of Criminal Justice in Huntsville (search "Reading With Conviction"). Each box cost me under $12, and comes with online tracking.

Fedex would charge me roughly the same amount for delivering a single ounce of mail. Overnight vs. maybe four days. I'll happily take the USPS service for this one, thanks.

Easy to curse the Post Office, but you couldn't do better. No, sorry, you couldn't.


Renee: Canada Post was not privatized. It became a Crown Corporation in 1981. The one thing that did change was that Canada Post could no longer automatically rely on subsidies to finance it's operations.

In 2000, lettermail rate increases were capped at 66.67% of the rate of inflation (which means that if costs increase more than inflation, Canada Post has to make up the revenue elsewhere and/or cut back on expenses).

I say bring on privatization if it means that 50-year old multi-floor sorting stations near railways (like the one in downtown Winnipeg) can be replaced with modern and efficient one-floor sorting stations at or near airports and major highways.

Canada Post has partially privatized it's retail services by placing outlets within private retailers, such as Shopper's Drug Mart.

Jason Goodman

Regarding "Fed Ex could do it better": while the postal service may have a statutory monopoly on ordinary letters, it also has a statutory obligation to deliver mail to anyone, anywhere in the U.S. If you're going to complain about unfair regulation, you need to look at both sides.

As for the impossibility (and economic utility) of checking every letter for a stamp: You're assuming that stamp-checking has a noticeable cost.

But stamp-checking isn't something done by some massive machine in a D.C. basement, and the U.S. Mail doesn't face the economic question, "should we spend $X billion to upgrade the stamp-checking machine to gain Y% accuracy?"

Stamp-checking is (at least partly) done by individual letter carriers picking up mail and dropping it off. They glance at the letters as they walk to and from their trucks. This is sort of a distributed system with no additional costs, but it does lead to uneven enforcement. Some letter carriers may let it slide, some may be hard-nosed by-the-book types.

And some (most) might let the occasional unstamped handwritten letter to your daughter pass by, but were you to start sending out *all* your mail unstamped, they'd take action.



I don't want to be a spoilsport, and this sounds like a fun idea, but isn't this probably a federal crime?

In particular, #1's suggestion sounds illegal, though brilliant. (Not something I'd lose sleep over).

Mike Scott

Certainly, in the UK the Post Office is legally required to attempt to deliver all mail, whether stamped or not, although they won't release an unstamped letter to the recipient until he pays for it. That's the way all post used to work, until the invention of the postage stamp to pre-pay postage in 1840.