Do (very) old stamps remain valid?

Stamps with a face value in Belgian francs will be invalid from 1 January 2028. Stamps with a face value in euros are valid indefinitely. You can use them to frank

• Non prior mail in Belgium.
• Mail for foreign addresses. In this case, affix a blue A Prior sticker as well.

The old stamps cannot be used for prior mail in Belgium (this requires a prior stamp with barcode). Parcels or registered mail cannot be franked with the old stamps either.