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HMRC internal manual

Compliance Handbook

How to do a compliance check: starting a compliance check: interaction between compliance checks and the SA enquiry window

Detailed guidance on the process to follow when opening an IT/CTSA/SDLT enquiry is contained in the relevant guidance. See

  • EM1506 for ITSA time limits and
  • EM1510 for CTSA time limits and
  • CH53100 for Stamp Duty Land Tax time limits.

Where risk information is going to be used for compliance checks into taxes that do not have a self-assessment enquiry framework, no IT/CTS A/SDLT enquiry need be opened. However, if the result of the compliance check is that the identified risk extends to IT, CT, CGT or SDLT, then it may be necessary to open an IT/CTSA/SDLT enquiry to address those risks.

Where the risk requires that an unannounced visit is necessary you should consider whether at the visit you are likely to review income tax, corporation tax or stamp duty land tax risks within an open enquiry window. If records relating to an open enquiry window will be checked and a notice of enquiry has not already been issued, an enquiry notice should be given to the person, with a copy for any agent authorised to act, at the same time as the notice advising of the visit.

If a risk exists for a chargeable period for which the enquiry window has closed and

  • it is unlikely the risk will affect other chargeable periods or
  • it is unlikely that risk will be identified by checking either a current chargeable period or a chargeable period for which an enquiry window is open

you can only address the risk if there is a potential discovery position.

There is a potential discovery position if

  • there is reason to suspect, see CH23560, that tax

    • may not have been assessed, or
    • may have been under-assessed, or
    • relief given may be excessive


  • if the suspicion turned out to be true you could make a discovery assessment to correct the tax position.

EM3200+ contains guidance on when and how it may be appropriate to re-open earlier years in an IT/CTSA check.