According to the group, many taxpayers who file self assessment tax returns are required to make payments on account.
The payment on account due by 31 July is the second instalment payment towards the 2020/21 tax bill, with the balancing payment due by 31 January 2022.
As part of the government’s coronavirus support measures in 2020, self assessment payments on account due in July 2020 were automatically deferred until January 2021.
However, LITRG has warned that is not the case for the second payments on account for 2020/21 which are due at the end of this month.
Victoria Todd, head of LITRG, said: “If you have already submitted your 2020/21 tax return, then your second payment on account amount will be recalculated by HMRC based on the information on the tax return and so the amount due on 31 July should be correct.
“Therefore, if you have not yet filed your tax return for 2020/21 you should consider doing so before 31 July.”
She added: “If you cannot pay the amount due, contact HMRC as soon as possible to discuss the possibility of paying the amount due in instalments.HMRC have indicated they will continue to treat all such requests sympathetically in view of the current economic situation.”