Would you know what law that was?
It's the
Capital Acquisitions Tax Consolidation Act 2003 s. 48A (which was inserted by the
Finance Act 2019). That section says that:
"A person who intends to apply for probate in relation to the estate of a deceased person . . . shall submit information to the Commissioners which information shall be specified in regulations made by the Commissioners"
The regulations made by the Revenue Commissioners say that the information to be provided includes:
"For each beneficiary, the aggregate of the taxable values of all prior gifts and inheritances received by that beneficiary within the applicable group threshold on or after 5 December 1991".
Running with T McGibney's example, Mary doesn't have to disclose to Bob's executors that she received 100k from Mick; she only has to disclose the total of all the gifts and inheritances she has received from all donors who are within the same group threshold as Bob.
If Bob is, say, Mary's father, she does't have to include anything she got from her uncle Mick, because Mary's father and her uncle are in different group thresholds.
If Bob and Mick are both uncles to Mary they're in the same group threshold, in which case she has to include the 100k she got from Mick. But all she has to say is that she has received X amount from donors with the group threshold since 1991; she doesn't have to say how many gifts or inheritance that represents or who gave any of them. The executor may have his suspicion that Mick provided some or all of the amount but he can't know that, not least because there is at least one other person in the threshold. And, if Bob left an inheritance for Mary, it's not impossible that he also gave her one or more gifts.
It goes without saying that the executor has no business telling anyone else in the family the information that Mary supplies. GDPR doesn't apply to Mary to prevent or excuse her from furnishing the information needed, but it
does apply to the executor to prevent them from using the information for any purpose other than the purpose for which it was supplied, and from disclosing the information unnecessarily.
Regarding Premos's query; the executor has to include this information in form SA2, which is part of the probate application process, so it has to be obtained before probate is granted. It doesn't matter whether the executor or the executor's solicitor asks for it. You should assume that any information supplied to the executor's solicitor is available to the executor anyway, since a solicitor normally doesn't — indeed, can't — keep information from their client.