In what way is it tax efficient? I thought it was the opposite because of the way inheritance tax bands increase if the "family home" is passed to offspring.
I guess it's tax efficient if they sell, give the money away, and try not to die within seven years though.
What's not clear in this OP is who owns the house and how is it owned. If it is owned as joint tenants, it automatically passes to surviving spouse and private is not needed to sell it.
However, if it was owned as joint tenants, there can be no inheritance for the offspring from the house sake as the deceased did not fully own a "share" to bequeath.
If it was owned as tenants in common, then the deceased can bequeath their share and the house probably needs to be sold to release the funds, unless survivor can buy the other half from the estate and give the beneficiaries their share that way (unless they come to some other agreement of course).
Mixed up in this is potential elderly financial abuse.
Questions are - why is the son acting as executor? Why is the son deciding the parent will live with them? Does the son have POA? If not, does anyone?
I think I'd be wanting to send a solicitor's letter to the son, if I was one of the beneficiaries, asking for detailed information and accounts to date.
If the parent is of sound mind, why aren't they questioning or resisting all this?