How do I change the postage price after an item has closed?

[cyberrootrat]

I have listed an item with the incorrect weight for postage and now that the item has sold I need to change the postage details in order to invoice the buyer with the correct postage. Is there a way that I can do this?

[cvok]

I love how completely hard line and intolerant the above comments are, when eBay often underestimates postage costs, and mistakes are made. If the difference is large then obviously there are considerations to be made but giving negative feedback after the seller has apologised for the mistake and the difference isn't too much is heavy handed and petty. The buyer should be reasonable. Postage is postage and the new postage cost will be confirmed on the parcel as being true.