Payments on account system glitch
The due date for making your second payment on account for 2018-19, was the 31 July 2019. The amount that was due for payment is usually the same as that for your first payment on account made on or before 31 January 2019. If you are late making a payment on account, you will likely be required to pay interest and penalties.
Issues with HMRC’s handling of payments on account have been reported by a number of taxpayers. This is an ongoing problem that also affected the first payment on account due in January 2019. If the first payment on account was missing, the second payment on account may also be affected. This is because HMRC did not correctly process all the payments on account information for 2018-19.
The glitch could have resulted in you not receiving the usual statement of account from HMRC telling you how much tax you needed to pay by 31 July 2019. HMRC has said that if you are affected, 'any liability for 2018-19 this will be payable in full in January 2020. Any payment intended for the 2018-19 POA, will be allocated against any 2018-19 balancing payment due on 31 January 2020'.
This could result in those affected having to pay a far larger amount than expected as a final payment for 2018-19 in January 2020. If you are affected by this glitch, please contact us and we can help you understand your available options, as making a 'voluntary' payment could result in further issues.
Source: HM Revenue & Customs | 29-07-2019