Gifting from USA to my 14 yr old.

My 14 yr olds step grandfather wishes to send her $100,000 whilst he’s still alive. Is it as simple as him sending it to her bank account and that’s it or do we need to let HMRC know etc and pay taxes ? Is it easier for her to have this as inheritance after he passes instead? He is pushing to do this now. Am stuck with what to do or who to ask !

Hi

From the UK, there are no income tax implications on the receipt of a cash gift unless the cash gift generates interest or dividends.
These would then potentially be subject to tax. Further guidance can be found here (Tax on savings interest and Tax on dividends).  

Thank you