First elected to the Legislative Assembly of Ontario in 1995 under the Progressive Conservative (PC) banner, Flaherty would sit as a member of Provincial Parliament (MPP) until 2006, also serving in a number of Cabinet positions from 1997 to 2002 during Premier Mike Harris' government.

Flaherty Dow Elliott & McCarthy LLP, as it is now known, is a law firm specializing in motor vehicle accident and personal injury litigation.

Flaherty ran for in the provincial election of 1990, finishing third against New Democrat Drummond White and Liberal Allan Furlong in the riding of Durham Centre.

[9] Flaherty was re-elected in the 1999 election in the redistributed riding of Whitby–Ajax, and was named Attorney General with responsibility for Native Affairs on June 17, 1999.

[9] In June 2001, Flaherty was evicted from his constituency office in a theatrical action by Ontario Coalition Against Poverty which aimed to bring home the effects of his policies.

[10] Flaherty ran to succeed Harris in the 2002 PC leadership election, but lost to frontrunner Ernie Eves, his predecessor as finance minister.

Flaherty's campaign featured attacks on Eves, calling him a "serial waffler" and a "pale, pink imitation of Dalton McGuinty".

[9][14] On June 13, 2005, the Canadian news website bourque.org reported that a meeting of prominent Conservative organizers and fundraisers had been held to plan for a Flaherty bid for the leadership of the federal party should Stephen Harper resign.

Flaherty resigned his seat in the Ontario legislature to run for the Conservative Party of Canada in the riding of Whitby—Oshawa, narrowly unseating incumbent Judi Longfield.

This marked the first time in Canadian history that a husband and wife have simultaneously represented the same electoral district at two different levels of government.

Flaherty said that income trusts would cost the government $500 million annually in lost tax revenue and shift the burden onto ordinary people.

[20][21] Diane Francis, editor-at-large for the National Post, urged that the rule changes be recanted, arguing that there were flaws in the policy which hurt Canadian investors.

John McCallum, the Liberal finance critic, asked Flaherty to explain the reasoning behind the change in income trust tax policy.

McCallum said "Your first problem is that having lured hundreds of thousands of ordinary Canadians into income trusts by promising not to raise taxes you then cut them off at the knees.

Given the minister's "current crusade on financial literacy", Fullard believed a suitable charitable cause would be a scholarship for business education.

Howe Institute, which stated: "This tax policy gem is very good news for Canadians, and Mr. Flaherty and his government deserve credit for a novel program.

It says he "enhanced his country's reputation for sound fiscal policy that takes full account of social justice, while a strong regulatory regime has kept the financial sector out of the chaos.

[35] Mississauga Mayor Hazel McCallion went further by issuing a challenge to Flaherty to publicly debate the need for permanent federal funding for the repair and upkeep of municipal roads and bridges.

[37] Flaherty said his office broke government contracting rules in hiring MacPhie & Company to help write the 2007 budget speech and provide advice on how to sell the document.

[38] On February 7, 2008, Liberal finance critic John McCallum formally called on Auditor General Sheila Fraser to conduct an audit into the untendered contract awarded by Flaherty to MacPhie & Company for work done in advance of the 2007 budget.

[40] David Curtain, who worked on Flaherty's Ontario leadership campaign, received $24,877.50 to write the finance minister's first budget speech.

Toronto family law lawyer Sara Beth Mintz, an Ontario Progressive Conservative Party vice-president, received $24,900 for budget "analysis, assessment and advice".

[43] Flaherty says he was unaware his former chief of staff broke government rules in handing a well-connected Tory an untendered contract to write the 2007 budget speech.

[44][45] The Foreign Account Tax Compliance Act is American legislation that requires cooperation, legal and financial, from Canada (and other nations), in order to be implemented.

[46] While announcing Economic Action Plan 2012 on March 29 in the House of Commons, Flaherty explained that, by February 2013, the government would be phasing out the penny.

He intervened in the 2013 Regina wastewater plant funding referendum, during which he wrote an open letter arguing that voters should select the P3 option.

The Budget contained a new Building Canada Plan for the construction of public infrastructure such as roads, bridges, transit and port facilities.

[1][55] At the time of his resignation, he held the honour of being the Longest continuous serving cabinet minister in a single portfolio in the 28th Canadian Ministry.

One colleague, Hamilton lawyer John Soule said, "He is a driven person ... and certainly is prepared to do what is necessary in terms of time and hard work to achieve what he believes is right".

[63] His wife, Christine Elliott, was the Progressive Conservative Member of Provincial Parliament for Oshawa–Whitby, east of Toronto and Deputy Leader of the Opposition until her resignation in August 2015.