As part of measures to contain COVID-19 and be able to tack and trace potential infection you may need to fill in a new form before or upon arrival back in Belgium from your holidays. All passengers aged 16 or older must fill in the form.
The 'Belgium_PassengerLocatorForm' must be completed by all passengers arriving in Belgium following a stay outside the Schengen Area, or, in a high-risk area as defined by the Belgian authorities and located inside the EU+ area. The UK is within the 'EU+' area.
Details of the current list of high risk/ red areas both for travel to and from Belgium within the EU+ area can be found here. In the UK only Leicester is a defined high risk area at the time of writing, but other parts of the UK are deemed 'orange' at the moment (Midlands, North East & Yorkshire, North West and Northern Ireland).
COVID testing and a 14 day quarantine are obligatory if returning from a 'red' zone and recommended if travelling from an orange zone.