Former Prime Minister Tony Blair and his lawyer wife Cherie avoided paying £312,000 in stamp duty on a £6.5 million house purchase in London.
The saving came to light among leaked documents called the “Pandora Papers”.
More than 12 million items have been scoured through by legions of journalists around the world.
According to paperwork, the Blairs bought the property in Harcourt Street, Marylebone in 2017.
It was for an office for Ms Blair’s business.
They bought the offshore company that owned it.
There is no suggestion of wrongdoing in the transactions.
However, previously Mr Blair had spoken out against tax loopholes.
He said they were “a haven of scams, perks, City deals and profits”.
And, in a 1994 speech, his first as Labour leader, Mr Blair said:
“Millionaires with the right accountant pay nothing while pensioners pay VAT on fuel.
“Offshore trusts get tax relief while homeowners pay VAT on insurance premiums.
“We will create a tax system that is fair which is related to ability to pay.”
In a statement to the BBC, Ms Blair said:
“It is not unusual for a commercial office building to be held in a corporate vehicle or for vendors of such property not to want to dispose of the property separately.”
The Blairs added that “the acquisition of a company comes with different tax consequences” and they “will of course be liable for capital gains tax on resale”.