If an enquiry into your tax return is in progress (that is, a notice of enquiry has been given by us and the enquiry has not been completed) and we form the opinion that:
- the amount of tax payable that is stated in your self-assessment is insufficient (that is, the amount is lower than it should be); and
- unless the assessment is immediately amended there is likely to be a loss of tax to the Crown (such as where we have reason to believe that the amount of deficient tax may not be paid once the enquiry is complete – see RSTP1006),
then we may notify you and amend your return to make good the deficiency.
We will also charge interest on the amount (or additional amount) of tax chargeable as a result of the amendment, backdated from the filing date of the return, until the amount is paid (see RSTP4002).
A notice of an amendment of a tax return during an enquiry is not a closure notice and does not close the enquiry (see RSTP1006).
If your tax return contains an inaccuracy, depending on the circumstances and the nature of the inaccuracy you may also be liable to a penalty (see RSTP3011).
Once we have notified you that we are making such an amendment you cannot then make your own amendment of our amendment, even if the time limit for you normally being able to do so has not expired (see RSTP1002).
You cannot give a notice of review (see RSTP6006) or appeal (see RSTP6008) in relation to a decision by us to amend your tax return while an enquiry is in progress and the enquiry has not been completed.
If we open an enquiry into a return which you have amended, and the scope is limited to matters arising from that amendment because a previous enquiry into the original return has been completed (see RSTP1003), then any amendment by us in these circumstances can only be made if the deficiency in tax mentioned above is attributable to the amendment that you made.
You must pay any amount or additional amount of tax (and, where applicable, interest) chargeable as a result of our amendment of a return during an enquiry immediately (that is, the same day) on receipt of the notice of amendment. Should you fail to do this, tax is due and payable to us and is treated in the same manner for debt enforcement purposes as if it were a self-assessment by you (see RSTP5001 for further guidance on debt enforcement).
If you fail to pay any tax (and, where applicable, interest) due in full by the date falling 30 days after the date by which the amount must be paid, then you are liable to a penalty for failing to pay tax on time (see RSTP3008).
RSTPA 2014 section 87