In a statement on his website he said was concerned that his tax affairs were “distracting” from the general election campaign.
Lord Ashcroft has donated £4,131,995 to the Conservatives.
He said: “David Cameron has said that anyone sitting in the legislature – Lords or Commons – must be treated as resident and domiciled in the UK for tax purposes.
“I agree with this change and expect to be sitting in the House of Lords for many years to come.”
Tory leader David Cameron said: “I'm glad this has been cleared up, now we can get on with the election campaign.
“Someone's tax status is been them and HM Revenue but I'm delighted he has come out and revealed his undertakings and status.”