What is the tax card valid for January?
In January 2020, you still continue using your 2019 tax card. The percentage rate on the card is the same as in 2019. However, the card's income limit is set back to zero.
Alternatively, you can request a revised tax card in MyTax, with 1 January 2020 as its start date of validity. Give the card to your employer well in advance of the first payday in January.