Johnson, who was born in New York and holds an American passport, decided to pay up ahead of a visit to Boston, Washington and New York next month.
This pay-out will help ensure the trip, which is intended to champion investment in London, will not be eclipsed by an ongoing row over his tax bill.
Last year the London mayor revealed he was being pursued by the US tax authorities for the sale of his first family home in North London for £1.2m in 2009. Commentators had said he could be facing a charge of around £100,000, but sources told the Financial Times the final amount was no where near this.
Mark Sher, a US tax specialist at American private wealth manager Maseco, had previously told City A.M. "He’s a citizen with a US passport, and therefore must pay US taxes. The possibility of him going to jail is minimal, because he’ll probably end up paying the tax. But if he doesn’t, jail becomes a very distinct reality.”