December

30         Online submission of personal tax returns for 2018/19 where taxpayer wishes to settle outstanding underpayments of tax of less than £3,000 as deduction through PAYE system

31         Corporation tax returns for accounting periods ended 31 Dec 2018

January 2020

14          Corporation tax third quarterly instalment payment for accounting periods ended 31 Dec 2019

17          PAYE cheque payments for month ended 5 January should reach HMRC by this date (22 Jan for electronic payments)