I was under the impression that PAYE NI is due by 22nd of the following month. I logged in to pay the NI on the HMRC website on 22nd Feb, after finding difficulty locating the Accounts office reference number [required on payment], I decided to pay it some other time. The page said that Month 10 NI (for period ending 05 February) is due by 22nd April 2018. Not sure why the due date is so much later than before. I just paid this today anyway, after payment it said that the payment is late and was indeed due by 22nd February. I have quickly stored a screengrab of the HMRC website giving the 22nd April due date to appeal if there are penalties imposed. But want to know which due date is the actual due date. The ltd company is a owner operator business. Only person on payroll is the director if that helps.