Payments on account for self-assessment are usually due on 31st July each year.
The payments due on 31st July 2020 are now deferred until 31st January 2021.
You don’t have to do anything for this change to take place – simply don’t pay your payment on account.
Please note, of course, that you do still need to pay the tax due, and in fact, the amount payable on 31st January 2021 will be especially high. It’s therefore good practice, wherever possible, to set aside the funds in a separate account.