From what I’ve read that doesn’t seem to be quite right. This article from the Daily Mail- http://www.dailymail.co.uk/news/article-5442861/Meghan-Markle-tell-tax-authorities-cash-secrets.html – says:
Meghan will have to tell the US taxman if she receives anything more than $100,000 (£71,600) from her fiancé or his family in the form of a royal allowance to cover expenses.
Nottingham Cottage – the grace and favor property in the grounds of London’s Kensington Palace where Meghan lives with Harry – may be taxed by the US if Markle’s presence in it is seen as a substitute for income before her marriage.
Meghan also has to give the US taxman full details of her finances if she and her husband-to-be have joint assets, bank accounts or offshore trusts in excess of $200,000 (£143,100).
The diamond engagement ring Prince Harry gave Meghan has been valued at over $100,000 (£71,600) by royal watchers. Because it is classified as a gift ‘from a foreign person’, Meghan would have to declare it to the IRS on a Form 3520 or suffer a $10,000 (£7,160) penalty.
I have a really hard time believing some of this, particularly the insinuation that the IRS is going to go after an engagement ring. Because that would mean that plenty of other rich Americans married to foreigners would have to be paying taxes on gifts from their spouse, and I sincerely doubt they are.