The EU Passport system is no longer valid to use in the UK.
As before your pet must be microchipped and either have an up to date Rabies vaccination or have been vaccinated at least 21 days before travel.
You will need an Animal Health Certificate to leave the country – this must be issued within 10 days of travel and is valid for one trip of up to 4 months.
Animals travelling to Ireland (North and South), Finland, Norway or Malta will also need a tapeworm treatment 24-120 hours before travel.
Returning to the UK you will need either a EU passport or a valid Animal Health Certificate and tapeworm treatment 24-120 hours before entering UK as before.