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Carriers reweigh and remeasure parcels in their automated sorting facilities after you buy the label. If the weight, dimensions, destination, or service on the label differ from what their equipment reads, you are charged an adjustment for the difference. The charge can arrive days or weeks after the package was delivered, and you can dispute it if you have photos of your packaging.
| Trigger | What the carrier found | Typical cause |
|---|---|---|
| Weight mismatch | The parcel weighed more than the label stated | Bathroom scale off by a pound, or you weighed the item but not the box and padding |
| Dimensional weight | The box's size priced higher than its actual weight | Large light box: carriers price by volume for air and express services, not just weight |
| Residential surcharge | The destination was a home, not a business | You declared a commercial address; many services surcharge residential delivery |
| Service mismatch | The parcel traveled under a different service than the label | You bought a USPS Priority label and dropped the box in a UPS drop box, or used carrier packaging for the wrong service |
| Address correction | The address needed fixing to be deliverable | Missing apartment number, wrong postal code, or a street name the carrier had to interpret |
Modern sorting facilities run parcels through automated dimensioning tunnels: the box passes under lasers and cameras that capture its exact length, width, height, and weight in a fraction of a second, then compare those readings to the label data. This is why adjustments feel random: your home scale said 4.8 pounds and their tunnel said 5.3. Both readings can be honest. Carriers bill in whole units and round up, and their calibrated equipment is the reading that counts. The adjustment is usually the difference between the service you paid for and the service your parcel's real measurements qualify for, not a penalty on top.
Adjustments are billed in batches, not in real time. The facility captures the data during sort, but the billing reconciliation can lag by days or weeks, especially with third-party label sellers (services like Pirate Ship or NetParcel pass carrier adjustments through to your account). So a package you shipped last month can still generate a charge today. This catches people off guard because the package was delivered long ago and they closed the mental books on it. Keep label receipts and packaging notes for at least a couple of months if you ship regularly.
Weigh the sealed package, not the item. Box, tape, padding, and the label itself all count. Measure the box's outside dimensions after sealing, because tape bulges and lids add real volume. Declare the destination type honestly. And use the right packaging for the service: putting a Ground Advantage label on a Priority Mail box is one of the most common service-mismatch triggers in the US, because the box itself signals a service. For Canada Post labels, measure carefully because dimensional weight kicks in on expedited and Xpresspost services for larger boxes.
Contact whoever sold you the label: the carrier directly if you bought from them, or the label reseller if you bought through one. Disputes work best with evidence: a photo of the package on a scale, a photo of the box with a tape measure, and the label receipt showing what you declared. File promptly, because resellers have their own dispute windows with the carriers and cannot reopen a case after it closes. Legitimate errors get corrected: a miscalibrated facility scanner is a known thing, and carriers do reverse charges when your evidence is clear. If you bought the label through a third party, expect the dispute to take longer than a direct carrier purchase, since the reseller has to argue your case to the carrier for you.
LetterAgent's shipping labels are Canada-only flat-rate Xpresspost for parcels up to 5 kg. Flat-rate pricing removes most of the classic adjustment triggers: there is no zone pricing and no dimensional calculation, because the rate is flat. But the 5 kg ceiling is real: a parcel over that weight cannot travel on a LetterAgent label at all. Get a quote from your AI assistant with the real weight and dimensions, approve the exact price, and you get the label PDF. If your parcel is close to the weight limit, weigh the sealed package on a proper scale first.
Ready to ship it? Get a shipping label with LetterAgent: describe it to your AI assistant, approve the exact quoted price, and get your label.
LetterAgent is a working name. Prices include print, postage, and our service fee. US prices in USD, Canadian prices in CAD (Canadian prices exclude applicable sales tax, added at checkout). Currently in private testing.
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