CH140290 | Interest: payments on account
From HM Revenue & Customs · Compliance Handbook
You must check whether, and from which date, the FA 2009 interest rules apply to the tax or duty you are dealing with. See CH140160 for full details.
HMRC charges late payment interest on amounts which remain unpaid after the due and payable date. This includes
Payments on account of income tax under section 59A TMA1970, and
VAT payments on account under section 28 VATA 1994,
Late payment interest applies to each individual payment on account and the balancing payment. This means that interest is charged on any POA amount which is not paid by the due date for the POA and on any balancing payment which is not paid by the due date for the balancing payment.