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Insufficient postage for accidentally using a USPS Flat Rate Box?

Hi ShipStation Community,

I recently got some dual-sided Express/Priority Mail boxes from USPS. I checked to make sure the Express side wasn't Flat Rate when I used it last week, but then forgot to check when I used the Priority Mail side to ship an order earlier this week. I just realized that it is in fact a Medium Flat Rate Box on the Priority Mail side, but I purchased regular Priority Mail postage on it, so the postage I paid would be $2 short.

I've emailed my customer to let her know that I would issue a refund to cover it if she has to pay additional postage, and also that I would get it to her in time for her event should it come back to me, but not knowing is causing me some anxiety as this is a time-sensitive order.

Has anyone had any experience with insufficient postage on ShipStation generated labels? I read on another website that if this happens with Click-N-Ship, the recipient won't get hit with a "Postage Due" notice and the shipper's account gets charged instead.

Does anyone know if has a way to charging our account instead of billing the recipient if this happens with a ShipStation label?

And has anyone ever had a package sent back for insufficient postage?

Thank you for reading my questions.


  • Robert@35EDDRobert@35EDD Member
    A Usual Suspect
    I have had this happen before but it wasn't by mistake. I contend that you should be able to apply priority postage (calculated by weight and size) to any box whether it is brown, priority mailing, or priority flat rate. The USPS rulebook is clear on this but many workers (even postmasters) will misinterpret. If you notice the writing on flat rate boxes it simply says "priority postage required". The part they are getting wrong is that flat, regional, and cubic rates are SUBSETS of priority postage that each offer some level of discounting. The sections that address flat rate discounts are specific about requiring the use of the appropriate box to qualify for those reduced rates. There is nothing in the document whatsoever that tells you that you cannot use flat rate boxes and pay the HIGHER price of standard priority postage (by weight and size). No one at the USPS, even higher ups at the regional offices can point me to a document that restricts this usage.
  • Aubrey@38122Aubrey@38122 Member
    A Usual Suspect
    Thanks for replying. I'd forgotten to come back and update this post on what happened with this shipment. Your point is interesting. The employees at my local Post Office always check if a package is in a Flat Rate Box if I drop off any packages. One time a clerk recommended someone pay $10 for Flat Rate when he could've shipped a few DVDs via Media Mail or regular Priority Mail for half that cost.

    Because my packages are usually under 1-2 pounds, it is usually cheaper to ship regular Priority Mail than Flat Rate.

    As for that package I wrote about last time, it would seem that USPS didn't notice -- or maybe because it was around Christmas-time, they didn't think it worth inconveniencing a customer or delaying a delivery for a couple of dollars. However, I will count myself lucky and make sure this doesn't happen again, because it was an anxious few days waiting to see what happened with that package.

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