So basically even though you opened the account in the 2020-2021 financial year you can use the same account, the only thing that changes is that the allowance resets on the 6th of April 2021.
Whatever you carried (let's say you deposited 5000 on 5th of April) it'll be carried automatically for the tax year 2021-2022 but it won't affect the allowance for 2021-2022? (e.g. allowance for 2021-2022 will remain 20000 but in addition to that you'll already have 5000 in your account from the previous deposit made in the 2020-2021 tax year)
Am I right?
Thank you,
/S