If you took the opportunity to defer your VAT payment due between 20 March and 20 June 2020 you now need to be thinking about making the payment.
This can be done in full – before 31 March 2021 – or by instalments. If you want to pay by instalments you need to apply, via your Government Gateway account, by 21 June 2021. The sooner you apply the greater the number of instalments you can have to pay it over.
See https://www.gov.uk/guidance/deferral-of-vat-payments-due-to-coronavirus-covid-19 for more information.