"If your adult passport was issued over 9 years ago, you may be affected. You should use this tool to check your passport is still valid for your trip before booking travel," says a notice on the Gov.uk guide to living in Belgium.
The online guide provides official information for British people moving to and living in Belgium, including EU Exit guidance, residency, healthcare and driving.
"Adult and child passports should have at least 6 months remaining from your date of travel. If you renewed your passport early, extra months would have been added to your new passport. These extra months will not count towards this so some passport holders will need to have more than 6 months remaining in order to travel," the notice adds.
The Brussels Times