SolvedCH53100 | Assessing Time Limits: Extended time limits: Overview
From HM Revenue & Customs · Compliance Handbook
During a compliance check, you may establish that
all taxes have not been assessed or accounted for, or
sums have been over-repaid or wrongly deducted.
You will need to decide what action you can take to recover this tax. That action may be an assessment, see CH51250, which must follow the assessing time limits outlined at CH51300.
In certain circumstances the time limits for assessing are extended beyond the normal time limit of 4 years from the end of the relevant tax period.
Relevant tax period is explained at CH51700.
The extended time limits are
6 years (careless) from the end of the relevant tax period, or
12 years (offshore) from the end of the relevant tax period, or
20 years (deliberate) from the end of the relevant tax period.
Whether you can use the 6 year or 20 year time limit depends on
the type of tax
whether the person’s behaviour, or that of a person acting on their behalf, has led to the loss of tax, or
whether the person has failed to comply with certain obligations.
The 6-year time limit only applies for income tax, capital gains tax, corporation tax, stamp duty land tax, inheritance tax, stamp duty reserve tax and petroleum revenue tax.
The 12-year time limit only applies for income tax, capital gains tax and inheritance tax involving offshore matters or offshore transfers.
You can find more information about the 6 year time limit in CH53300, the 12 year time limit in CH53510, and the 20 year time limit in CH53600.
There are other time limits for indirect taxes and assessing penalties, see CH53150.