I don't think it works like that, I'm afraid. I'm a bit wobbly on IHT but I think that, although if your grandfather were to give you �3000 a year it would be exempt for IHT purposes, a single gift of �25000 would, as far as i know, not even get that. Your grandfather's estate would be calculated as if the whole �25000 was still part of it. As for paying for part of the property, rather than simply giving you the money, I think you're right; he would acquire an interest in the property which would form part of his estate for tax purposes. Try HMRC's Inheritance tax helpline - 0845 3020 900