Insufficient Postage On First Class Large Envelope--What Happens?

If I use a home kitchen food scale to weigh a first class large envelope and there ends up being a discrepancy between the reading on my scale and the USPS scale and I am short let's say 15c in postage, what happens to the envelope and all the stamps on it? Are the stamps cancelled and then is the envelope returned to me marked "insufficient postage" and I am out all the stamps, or is the envelope mailed to recipient with postage due?

If a USPS employee thinks my first class large envelope is too rigid or thick and then itbecomes a package, what happens to all the stamps I put on the envelope? Are they cancelled, returned to me with insufficient postage, or is the now package still mailed to the recipient, but with postage due for the recipient?

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If you are using a (cheap) spring-based kitchen scale, do not start with an empty scale.

Put some weight on the scale - eg, to 25-50% of its range - and then add your package.

I suspect that most envelopes & flats will go flying thru, as long as they have some postage on them, because no one in management wants an employee costing north of U$D 20 per hour (more than U$D 65c per minute) stopping to figure a few cents postage due that another employee costing north of U$D 20 per hour (more than U$D 65c per minute) has to account for & collect.

Cheers,

/s/ ikeyPikey

You really need to pay attention to the thickness more than weight. They use a simple go / no go gauge.

Given you have to present packages 13 ounces or higher, you are not dealing with a lot of weight. Rounding up should take care of any risk.

The one package I had returned was due to overweight (postage was correct) and I could reuse but suspect handling at the post office may vary.