CTM35170 | Income Tax: collection of tax on annual payments: due and payable date on assessments
From HM Revenue & Customs · Company Taxation Manual
Tax due on an assessment under CHAPTER15 is due (subject to any appeal) within 14 days of the issue of the notice of assessment unless due earlier under ITA07/S949, S957 or S950, see CTM35120, CTM35135 and CTM35140.