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A parcel with too little postage is usually held, returned to the sender, or delivered only after someone pays the shortfall plus a handling fee. Which outcome you get depends on the carrier, whether a return address is on the parcel, and how large the shortfall is, so prevention is far cheaper than any of those endings.
Canada Post may return an underpaid parcel to the sender, hold it at a depot for pickup on payment, or deliver it and collect the amount owing from the recipient. A parcel with no return address has nowhere to go back to, so it can end up in the undeliverable mail stream, where it may be opened to find an address or eventually disposed of. None of these outcomes is quick: a returned parcel travels back through the system, which can take as long as the original trip.
The shortfall is not the only cost. Carriers commonly add a handling fee on top of the missing postage, and the recipient, asked to pay for a parcel they did not send, may refuse it. A refused parcel is then returned to the sender, who pays again or loses the shipment. For a gift, that is an awkward surprise; for a sale, it is a lost customer and a second shipping bill.
| Situation | Likely outcome | Cost to someone |
|---|---|---|
| Return address present | Parcel returned to sender | Return trip plus a new label to resend |
| No return address | Held, then undeliverable stream | Possible loss of the parcel |
| Delivered on payment | Recipient pays shortfall plus fee | Fee on top of missing postage |
| Recipient refuses to pay | Parcel returned to sender | Two trips, no delivery |
The usual causes are a wrong weight, a wrong size, or a label bought for a different service than the parcel needs. A bathroom scale that rounds down, a parcel weighed without its box and padding, or a box measured before it was taped shut can all understate the real figure. Another common cause is guessing: a parcel that looks light but is dense, like books, fools the eye every time.
Flat-rate labels remove one cause of shortfall, because the price does not change with distance. They still have limits, though: a flat-rate label covers parcels up to its stated weight and size. A parcel over that limit is not covered by the label, even if the label itself was paid in full. Weigh the finished, sealed parcel, not the contents alone.
Once a parcel is in the system, you cannot top up its postage from home. If tracking shows it held or returned, wait for the carrier's notice: it will say whether to pay at a depot, collect it, or let it return. Contact the recipient early if delivery on payment is likely, so they are not surprised at the door. And if the parcel comes back, fix the weight and label before resending, rather than reusing the same label, which will shortfall again.
A label bought through LetterAgent is quoted up front for the parcel you describe, so the shortfall risk sits in describing the parcel wrong, not in the label itself. If the parcel stays within Canada and under 5 kg, you can get a Canada Post Xpresspost label by asking your AI assistant: you approve the exact quoted price, pay once through Stripe, and get a label PDF to print and attach.
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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