The European Commission presented on December 19th 2018 a “no-deal” Contingency Action Plan which calls upon the EU Member States to act and get prepared for a hard Brexit after March 29th 2019.
As far as social security is concerned the Commission calls upon Member States to take all possible measures to ensure legal certainty and to protect the rights acquired by EU27 citizens and UK nationals who exercised their right to free movement before 30 March 2019.
UK home country workers that are temporarily seconded to Belgium are currently (until March 29th 2019) in application of EU Law and in accordance with the A1 form subject to UK social security law and therefore exempt to Belgium social security.
To avoid chaos Belgium as well as the UK could continue to apply the old EU rules even if these are no longer applicable by each enacting in their own jurisdiction a similar Statute.
This seems to be what the Commission wants to have achieved by all EU 27 Member States and the UK. The question remains whether there will be sufficient time to implement all this.
Prime Minister Michel announced on January 16th 2018 that his government would lodge a draft bill to prepare for Brexit. We expect there to be measures that will allow UK home country workers seconded to Belgium to remain on their home country social security if there will be a hard Brexit. Belgium will be ready. The question remains today will the UK be?