Can I change the dimensions of the shipment after generating a shipping label in the Parcel Manager?

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If the shipment has already been confirmed and paid for, it cannot be edited. If you click "Prepare", the shipment will receive the status "created" - then you can edit its dimensions. After generating a shipping label, you cannot change the parcel size. In this case, you should cancel the generated label and create a new one.

If you use Quick Send and want to change the shipment details, cancel the label using this form by selecting the option "I want a refund for an unused label". Then pay for and generate a new label.