Deceased persons: definition of period of administration
The period during which the personal representatives are settling the estate is called the period of administration. It starts on the day following the date of death of the deceased person and ends when the personal representatives have taken all the steps necessary to complete the administration of the estate.
The question of when an administration period ends is essentially one of fact and will depend on individual circumstances. It may in some cases coincide with the date when the residue of the estate can be identified. Sometimes the date of issue of the Inheritance Tax clearance certificate is taken as the date the administration was completed.
You should normally accept that the administration ended on the date the personal representatives tell you it did.
Detailed guidance is at CG30700 onwards. Any difficulty or dispute about the date of completion of the period of administration should be referred to HMRC Administration of Estates Cardiff for advice.