Taken directly from the Elections Canada website:

The Constitution of Canada requires that federal electoral districts be reviewed after each decennial (10-year) census to reflect changes and movements in Canada's population. As a result of the review, electoral district boundaries might be changed and new districts created.

The most recent federal redistribution process began in October 2021. First, the Chief Electoral Officer was tasked with applying the representation formula set out in the Constitution to recalculate how many members of Parliament (MPs) needed to be assigned to each province, and the new calculation was published in the Canada Gazette. The process of redistribution was then turned over to independent electoral boundaries commissions, which worked separately in each province to review the electoral boundaries and revise them, if necessary

On June 23, 2022, Parliament amended the representation formula.  The revised legislation ensures that every province retains at least the same number of MPs that it had previously been assigned - in other words, the number who elected in 2019.

The decennial redistribution for the 2020s exceptionally required two Representation Orders, one for Quebec and another that covered the other nine provinces.   In September 2023, the new Representation Orders were published in the Canada Gazette.

New Federal Electoral Map for Ontario Tabled in the House of Commons

London, Friday, February 10, 2023 – The report by the Federal Electoral Boundaries Commission for Ontario, outlining its proposed changes to the province's federal electoral map, was tabled in the House of Commons today. The report, which was sent to the Speaker of the House through the Chief Electoral Officer of Canada, will be reviewed by the House of Commons Standing Committee on Procedure and House Affairs.

The Commission was tasked with proposing new boundaries that, as best as possible, maintain population equality while taking into consideration social and geographic factors, including respect for communities of interest or identity and historical patterns of previous boundaries. These criteria, along with the submissions and the public feedback gathered at public hearings held between September 26 and November 8, 2022, all factored into the report tabled in the House today.

"The time and effort committed by the public to this important democratic process was remarkable and very much valued by the Commission. We are satisfied that we have balanced our statutory obligations with the views of the people of Ontario, striving for the goal of effective representation", said the Honourable Justice Lynne C. Leitch, Chair of the three-member Commission.

To consult the report and for more information on the next steps in the redistribution process, visit www.redistribution2022.ca.

Consists of:

1. the Town of Georgina;
2. that part of the Town of Whitchurch-Stouffville described as follows: commencing at the intersection of Bethesda Road and the easterly limit of said town; thence northwesterly, southwesterly, generally southerly and generally northeasterly along the easterly, northerly, westerly and southerly limits of said town to Highway 48; thence northerly along said highway to Bethesda Road; thence easterly along said road to Ninth Line; thence northerly along Ninth Line to Bethesda Road; thence easterly along said road to the point of commencement;
3. the townships of Brock, Scugog and Uxbridge; and
4. the Indian reserves of Chippewas of Georgina Island First Nation and Mississaugas of Scugog Island.