The Brexit transition period ends on 31 December 2020 and currently no post-Brexit trade deal has been agreed. Consequently, the arrangement which allows UK banks to trade in the EU (known as "passporting") will expire at the end of the year.
A number of UK banks have already informed their customers who live in the EU that they will lose their UK accounts at the end of 2020. More banks are expected to follow.
If your bank advises you of the impending closure of the UK account into which your pension is paid, then you must complete a World Link Mandate Form: