Determinations are issued by HMRC where a taxpayer fails to file a tax return. For example, a determination can be raised against an individual for failure to file a self assessment return (SA100) or against a company for failure to file a corporate tax self assessment return (CT600).

The determination is based on an HMRC estimate of the amount of tax due. In arriving at an estimate, HMRC will take into account the information that is available to it. For example, HMRC may consider comparable businesses or corporate information.

Unless the determination is superseded by a self assessment, it has effect for the purposes of payment of tax, collection and interest on unpaid tax as if it were a self assessment. This means that the due date for payment is the date which would have applied if the return and self assessment had been delivered by the filing date. Issuing a determination also gives HMRC the opportunity to commence formal proceedings for the recovery of the late paid tax.

There is no appeal procedure