What is this tag/stamp on a card from Hong Kong

[helent]

I got this card from Hong Kong which had this tag attached at the side.

It has some numbers on the address side.

Does anyone know what this is?

I feel like I saw something about this on the forum before, but I can’t find it.

[anon12838227]

This is a Postage Due stamp also called ‘T’ stamp. There is a post about it here:

No Stamps, Postage Due

Hi all, I’ve had a good look on the forum and couldn’t find a clear answer. I received an offical postcrossing card with ID from a neighbouring European country, but no postage stamp(s) where affixed. The postcard recieved a postmark and T sticker (Terminals Due?) with what looks like €2.13 to pay. The card was delivered when I was at work, but no attempt was made by the postal worker to collect this fee. I don’t mind registering the card, but should I let the moderators or admin team aware…

[helent]

Thank you!

[anon12838227]

I found more information about this from the UPU manual, I took a screenshot of the relevant portion:

[helent]

Interesting! I definitely did not have to pay anything, and it’s hard to believe the cost of recovering one or two HK dollar is worth it. Make sense for a package, maybe.

[iamfromhk]

Surface mail costs $4.60, while air mail costs $4.90.
Perhaps the sender didn’t use sufficient postage.