Payment on Account due 31 July
Your second payment on account for 2021 is due on 31 July 2021.
The payment on account is calculated as half your tax that you had to pay in the previous year. But that may have been calculated based upon pre-covid profits.
So will your tax for 2021 be as high as for 2020?
If not then you can reduce your payment on account at the end of July. Its better not to pay it than pay it and have to wait for the tax to be refunded after your tax return is submitted.