Second homes and buy-to-let, compared

All three nations charge more for an additional property, but the mechanism is structurally different in each — not just the rate.

Additional-property mechanism by nation
Nation	Mechanism	Threshold
England & Northern Ireland	An extra 5% on top of each standard band's own rate	£40,000+
Scotland	A flat 8% of the whole price at once (the Additional Dwelling Supplement)	£40,000+
Wales	An entirely separate, higher band schedule	£40,000+

In practice this means the same price can attract very different additional-property charges in different nations, for reasons that have nothing to do with the headline rate — see each nation's own rates page for the exact figures, or use the calculator directly.