War tax due stamp

War tax due stamp is a kind of war tax and postage due stamps that was used for mail when the war tax has not been paid by the sender.

[1] During war the sender of a letter paid a war tax.

Then they placed a war tax stamp on the letter showing the tax was paid.

If the sender did not do that, a war tax due stamp was applied by the postal service.

When the letter was delivered the person receiving the letter paid double the normal rate.