I have a residence card, registration certificate or confirmation of permanent residence under the EEA Regulations – how long can I continue using it?

Until 31 December 2020, when this document becomes obsolete and will only have residual value.  You should try to apply by 31 December for a new confirmation of your status – or (for non-EU family members) a Residence Permit – under the EU Settled Status scheme (EUSS).  If you don’t the Home Office plans to legislate to allow you to benefit from your EU free movement rights so long as you haven’t lost those rights through absence from the UK of more than 5 years, and you make an application under EUSS by 30 June 2021.