by mullet on Sat Nov 05, 2011 1:35 pm
By enquiry do you mean an enquiry under Section 9A TMA 1970? If yes, then HMRC have no time limit at all to conclude the enquiry and amend your tax return to create the charge. But you do have recourse to the Tribunal if you think that the enquiry is taking too long - you can ask them to direct that the enquiry is closed. But HMRC would still make the amendment in whatever figure is deemed appropriate.
If they are looking at your tax return under the "discovery" provisions, then they are using Section 29 TMA 1970. They would have had until until 05-04-2011 to raise an assessment under the normal time limit, until 05-04-2013 if your behaviour was careless, and until 05-04-2027 if your behaviour was deliberate.
If you owe HMRC money, then it makes sense to make a payment on account to contain the amount of interest that you will have to pay.