Phone prefixes in Markham, ON

In numbers

In-service prefixes

82

Telephone numbers covered

820,000

Carriers

18

Area codes

4

Provinces and territories

1

First assignment

January 31, 2000

Most recent assignment

February 27, 2026

Markham’s share of its area codes

Within area code 365, Markham accounts for only 51 of 706 prefixes (7.2%): the code is dominated by Markham and spread over 88 rate centres. Within area code 289, Markham accounts for only 16 of 772 prefixes (2.1%): the code is dominated by Hamilton and spread over 87 rate centres. Within area code 905, Markham accounts for only 11 of 773 prefixes (1.4%): the code is dominated by Hamilton and spread over 94 rate centres. Within area code 742, Markham accounts for only 4 of 148 prefixes (2.7%): the code is dominated by Brampton and spread over 68 rate centres.

Who holds these numbers

Iristel Inc. holds the largest share at 48 prefixes, 58.5% of the total, ahead of 17 other carriers. Code by code: in 365, Iristel Inc. leads with 44 of 51 prefixes ahead of 6 others; in 289, Iristel Inc. leads with 4 of 16 prefixes ahead of 9 others; in 905, Rogers Communications Canada Inc. (Cable) leads with 5 of 11 prefixes ahead of 2 others; in 742, Fibernetics Corporation leads with 1 of 4 prefixes ahead of 3 others. No carrier holds prefixes in every one of Markham’s 4 area codes, while 12 appear in just one.

Wireless and wireline

None of Markham’s holders carries a mobility brand in its registered name: all 82 prefixes belong to wireline or wholesale carriers, among them Iristel Inc, Rogers Communications Canada Inc. (Cable), Bell Canada and Fibernetics Corporation. A call showing a Markham number therefore nominally comes from a landline, cable or VoIP platform rather than a locally assigned cellphone.

How the allocation was built up

Markham’s dated assignments run from 2000 to 2026. The busiest period was 2015–2019, when 24 prefixes went to 6 carriers. 4 prefixes (5%) carry no date in the register: these are the historic pre-1999 assignments, the wireline bedrock of the rate centre. Since 2020 another 33 prefixes have been added, so the rate centre is still growing.

Markham’s oldest prefixes, the ones the register leaves undated, belong to Bell Canada: this carrier made up the landscape before competition arrived. The first dated assignment went to Rogers Communications Canada Inc. (Cable) in 2000. The most recent arrivals are Cogeco Connexion Inc. (2026), FGLTEL Inc. (2022) and Beanfield Technologies Inc. (2021), a sign that new carriers are still asking for numbers in Markham.

Markham’s 82 prefixes provide 820,000 numbers, which corresponds to a mid-sized city or a well-established suburb that every major carrier wants a slice of.

Iristel Inc. leads with 58.5% of the prefixes, but 17 competitors have set up in Markham: a market where the incumbent keeps the edge without exclusivity.

Demand remains steady: 42.3% of the dated prefixes go back to the last ten years, the most active period being 2015–2019. The rate centre is growing at a regular rather than explosive pace.

4 undated in the register.

Dialling a Markham number

Markham is served by 4 overlaid area codes (365, 289, 905 and 742). A 742 number is no more “out of town” than a 365 one; from abroad, dial +1 and the full ten digits.

The numbering neighbourhood

Markham shares area codes 365, 289, 905 and 742 with at least 20 other rate centres, including Hamilton, Brampton, Oshawa, St. Catharines-Thorold, Oakville, Ajax-Pickering, Cooksville and Thornhill. The largest of them, Hamilton, holds 222 prefixes in 289, 365, 742 and 905; the smallest on the list, Maple, has just 28.

What a Markham number tells you

A number attached to Markham tells you that its prefix was issued to a carrier for this rate centre in Ontario, most often Iristel Inc.. It does not tell you where the handset is today: a subscriber may have ported the number to any of the 18 carriers present here or to a VoIP service usable anywhere. Nor does it tell you who is calling: caller ID can be spoofed, and an Ontario area code is easy to borrow to look local.

Reading a register entry for Markham: code 365-360 is recorded for Iristel Inc., so every 365-360-XXXX number (10,000 possible) descends from that assignment. “Markham, Ontario” there names a rate centre, not a municipality, and several area codes overlay it.

Every Markham prefix

Each row is an in-service central-office code recorded for Markham, with its original holder and year of assignment.

What people check and report about Markham numbers

Searches typed into this site's lookup form since July 28, 2026, plus the verdicts and moderated reports visitors left. A search usually follows a missed call.

Had a call from a Markham number?

No clear pattern in reports on these numbers yet. If a call worried you:

1. Call back on a number you trust

   If a caller says they are your bank, the Canada Revenue Agency, a courier or your phone company, hang up and call the organization on the number from its website or your statement, never the number that called you. Caller ID can be faked.

2. Report the fraud

   Report the call or text to the Canadian Anti-Fraud Centre online or at 1-888-495-8501. If you lost money or gave out personal details, tell your bank first, then your local police.

   Report to the Canadian Anti-Fraud Centre ↗

3. Register on the National Do Not Call List

   Registering a landline or mobile on the National DNCL is free. Registered charities, political parties, newspapers and companies you already do business with may still call.

   National Do Not Call List ↗Who can still call you ↗

4. Forward suspicious texts to 7726

   Forward a scam or spam text to 7726 (SPAM on the keypad). It's free, and your carrier uses it to block the sender. Don't tap links or reply.

   Get Cyber Safe: forwarding to 7726 ↗

Allocated prefixes

All 82 in-service prefixes, grouped by rate centre.

Elsewhere in Ontario