A second home refers to any property you own that isn’t your main home. This could be a buy-to-let, a house you’re buying for a family member, or a holiday home for example. So, if you were a part-owner of your son or daughter’s new home, you’d have to pay the higher rate of Stamp Duty tax.
If you already own a home abroad and are buying your first home in the UK, you will be subject to incremental Stamp Duty. However, if you are buying your second home abroad, you’ll be subject that country’s Stamp Duty laws.