This query has 2 dimensions. First, HMRC. Secondly, father and son.
1 HMRC. The previous thread highlighted the (regrettable) lack of substantive and procedural law, and guidance, on revocation. But I agree with Malcolm that a claim which must be made by both parties surely cannot be revoked by one alone. The law anticipated that valuations could affect both parties (CG16400) but there is nothing like the CGT Regulations 1967 for hold-over claims.
Here the claim appears not to have been submitted yet. We are not told who holds the signed original form. The father could submit it, if he has it, but if the son tells HMRC that he rejects it HMRC might refuse to process it as their most neutral stance. They will want to stand aside from the family dispute as in rectification claims.
2 Father and son. It seems likely that the father had an expectation that the son would join in the claim and would suffer detriment if it were not made; and that was communicated to the son since he signed the form. The father may well have grounds to seek rescission of the gift. The arguments are as follows, in outline to avoid a legal treatise:
(a) promissory estoppel. Generally involves an anterior contract but not always and a deed comes close, as it makes binding a promise without consideration. Also, but not always, it must be a shield not a sword. Father could refuse to transfer the legal title if he has it. If the father refuses to pay the tax the son may be made to do so and then the father could dispute his right to recover under s282 (2) TCGA.
(b) conditional gift. The claim was a condition and is unfulfilled.
(c) unconscionable bargain. Particularly if the son has induced the father by agreeing to claim and now seeks in effect to deceive him so equitable fraud.
(d) mistake. The father justifiably thought the son would claim and the son’s reneging is equitable fraud.
I suspect a judge would strive hard to find a way of granting rescission if satisfied that the son does not have clean hands and is guilty of urine extraction.
3 As ever, much will depend on the facts and crucially the evidence. The deed is silent (? not even a helpful recital). Did the son execute the deed (not essential but helpful)? At risk of being a wiseacre I always spelled out in a deed of gift any consequential obligations of either party e.g. registration, tax filings, burden of related cost, default consequences, and made the donee execute also where these obliged him. Some of these might conceivably be implied by law.
Making the son formally aware of the consequences may well exacerbate family politics but the threat of action and costs may encourage him to change his mind. The law reports are replete with internecine family disputes over money when enough of it is at stake. There may not be mileage in threatening if action is not genuinely contemplated as it might make matters worse.
Jack Harper