Interest, penalties and surcharge: interest: concessional dates
The statutory due date is normally also the relevant date (RD) for interest purposes. However, there are a limited number of situations where as a concession the relevant dates can be deferred.
Generally a concessionary relevant date will only apply where HMRC has failed to make timely use of information supplied by the taxpayer. For example, issuing a return late (on or after 31 July following the end of the tax year to which it relates). However if taxpayers fail to meet their statutory obligations, for example failure to notify chargeability, interest will be charged from the statutory due dates.
The Department has the discretionary right to review the basis of assessment for the two years prior to cessation. It may result in the use of actual rather than the preceding year basis, but only where the aggregate of assessable profits is higher using the actual basis of assessment.
Any additional tax due is collected by Revenue assessment, with the relevant date for interest being 30 days after issue of the assessment.