1911 to 1972

In 1956, Canada, the United States, and Mexico came to an agreement with the American Association of Motor Vehicle Administrators, the Automobile Manufacturers Association and the National Safety Council that standardized the size for licence plates for vehicles (except those for motorcycles) at 6 inches (15 cm) in height by 12 inches (30 cm) in width, with standardized mounting holes.^[6] The 1954 (dated 1955) issue was the first Ontario licence plate that complied with these standards.

1973 to present

After 1973, Ontario ceased to issue plates annually. Instead, validation was indicated by means of stickers affixed to the top right of the rear plate. All Ontario license plates issued since 1973 remain valid for display.

In 1973, the "Keep it Beautiful" slogan was introduced to Ontario passenger plates. In 1982, the slogan was changed to "Yours to Discover". The adjustment was made to reflect the province's new tourism campaign.^[9]

In April 2019, the Government of Ontario announced that the plates would be redesigned. The plates' design includes a superficial laminate layer manufactured by 3M.^[10] The plates have a two-tone blue background with white letters and numbers flanking a stylized white trillium, and no longer embossed. The motto was also changed to "A Place to Grow", taking inspiration from Ontario's unofficial anthem "A Place to Stand, a Place to Grow".^[11]

Issue of the new plates began in February 2020. The new plates faced criticism from law enforcement agencies, as their new design made them difficult to read in certain lighting conditions. Concerns were also raised that photo radar systems would have difficulty reading them, due to the lighting issues, as well as the smaller sizing of their "Ontario" text. On February 20, 2020, Premier Doug Ford stated that the government planned to recall the initial batch, and was working with 3M on improvements.^[12] However, on May 6, 2020, a spokesperson for Ford announced that the blue plates would be discontinued entirely after "thorough testing by law enforcement and other key stakeholders". The previous white plates were reinstated, with their coating also made more durable, although the blue plates continued to be issued through early-June until their supply was exhausted.^[13][14]

Serial numbers reserved for government officials

Green vehicle plates

Historic vehicles

Historic vehicle license plates were introduced in 1969 as yearly plates. In 1973, plates switched to permanently issued plates validated with stickers.

Vehicles more than 30 years old and substantially unchanged since manufacture may qualify for a "Historic" registration.^[24]

Annual fees were much lower ($18 vs $120 for a passenger car until 2022),^[25] but historic vehicles may not be used as conventional transportation. They legally may only be driven to and from events and parades where the vehicle is on display, to garages for maintenance, and other similar use cases. Annual renewal stickers are affixed to the rear plate, as with passenger vehicles.

Historic plates are not to be confused with year-of-manufacture plates.^[26]

1916 to 1962

Commercial license plates were first introduced in 1916.

1963 to 1979

In 1963, Ontario switched to a quarterly system for commercial plates. Plates could be issued on a quarterly basis rather than paying for a full year of registration.

• This 1963 Ontario commercial license plate was the first quarterly plate. It expired in March 1964 and until dated March quarterly plates appeared in March 1967 this plate when issued in December 1963 was used as a quarterly commercial plate.
• In 1965 all June, September and December quarterly plates were issued in the reverse colors as in 1963 and 1964. In alternate years Ontario quarterly plates reversed their colors each year.
• First issue of commercial quarterly plates dated for March.
• Each plate would be valid for three months or a quarter of the year. This plate was issued in June 1969 and expired in September 1969.
• Quarterly plates had several serial format arrangements. Beginning in March 1968 they switched to the
  A1-234, 123-4A and A12-345 & 123-45A formats.
• Final quarterly plate issued. Ontario switched to plates renewed with stickers in 1980.

1980 to present

In the 1980s, Ontario shifted to plates that were renewed yearly with stickers, ditching the quarterly system.

Prorate plates

Used on vehicles registered in the International Registration Plan (IRP).

Bus plates

Bus license plates were first issued in 1973. They followed the quarterly system until 1980, switching in favour of a new permanent plate renewed yearly with stickers.^[28]

School Bus plates

School Bus license plates were first issued in 1975 under a yearly registration. Unlike regular bus license plates, these plates expired in June at the end of the school year. In 1980, these yearly issued plates were phased out for permanent plates revalidated with stickers annually.^[28]

Farm plates

Farm plates were introduced in 1978 using the quarterly system. In 1980, the plates were switched to permanent plates revalidated with stickers.^[28]

Vehicles over 3000 kg owned by farmers and used for farm-related purposes, such as working the soil, building maintenance, and the transportation of farm products, may qualify for a farm plate. Farm-plated trucks and towed trailers may also be used by a farmer for personal transportation.

To qualify, a farmer must meet a series of criteria, including membership in farming organisations and a minimum amount of income that derives from farming. Fees for farm plates are substantially lower than for passenger or commercial plates. The Highway Traffic Act also exempts farm vehicles from several requirements imposed on commercial vehicles.^[29]

Farm plates are black on white with a black crown separator, in a pattern similar to commercial plates. They have the word "FARM" written vertically on the left of the plate. Validation stickers are the same as for other vehicles, and are affixed to the front plate, as with commercial plates.

1921 to 1973

Trailer plates were first introduced in 1921. Plates issued from 1921 to 1929 had the letter T at the front. In 1930, the letter T was moved to the end of the number. A quarterly system was introduced for trailers starting in 1963.^[28]

1973 to present

By 1973, the quarterly system was phased out in favour of a semi-permanent plate validated each year with an annual sticker. As of 1980, trailer plates no longer require yearly validation stickers, rather a one time fee.^[28]

1911 to 1980

1980 to present

Off-road vehicle plates

These license plates are issued to ATVs and other vehicles for off roading uses.

Moped plates

Snowmobile plates

This section needs expansion with: December 2022. You can help by adding to it. (December 2022)

Unlike all Ontario license plates — which were changed to reflective plates in 1994 — the snowmobile plates remain non-reflective.

1927 to 1972

Motorcycle Dealer plates

Dealer plates for motorcycles have been issued since the 1920s.^[28] Very few of these early plates were issued, thus making it a rare plate. The 'M' prefix was featured on all plates before 1973. From 1973 to 1979 they were issued with the 'DL' prefix, with a similar design to regular Motorcycle plates. In 1982, the government began issuing permanent plates with yearly registration stickers.^[28] Reflective plates were introduced in 1994.

The current plate design is a white serial on a light blue plate. These plates are the same size as regular motorcycle plates. The serial format used by these plates is AB123, running from AA001 to AF965 (as of February 23, 2020)^[17]

Medical doctor plates

This section needs expansion with: December 2022. You can help by adding to it. (December 2022)

Medical doctor plates were first introduced in 1930, and are denoted by the letters starting with MD. When all the MDA - MDZ serials had been issued in the late 1990's ^{[date missing]}, new serials using MAA started being issued.

Amateur radio plates

Amateur Radio plates were introduced in 1969 as supplemental plates. In 1976, Ontario permitted the call-sign to be on regular passenger plates, eliminating the small supplemental plates.^[28]

Special Event Plates

This section needs expansion. You can help by adding to it. (August 2022)

Veteran Plate

License Plate Graphics

This section needs expansion. You can help by adding to it. (August 2022)

Plates with graphics are also available.^[41] Graphics first being issued on license plates began in 1996. The variety of graphics includes charities, universities, community organizations and popular Ontario sports teams, such as the Ottawa Senators. All plates offer the French slogan since 2017.^[28]

Discontinued Graphics

Certain graphics have been discontinued and are no longer issued. A plate design is considered discontinued once it is no longer offered at ServiceOntario.

Alternative supplier

In 2016, an increase in the rate of defective plates combined with an increase in the number of registered vehicles led to the Ontario Ministry of Transportation becoming unable to keep up with demand for plates. It placed an order for 100,000 units from the Waldale Irwin Holdson Group, the largest licence plate manufacturer in North America.^[49] Plates are produced by the Waldale Manufacturing facility in Amherst, Nova Scotia.

Plates from the first batch of 35,000 can be identified due to the use of embossed letters and numbers from Nova Scotia plates, which differ in appearance from Ontarian fonts.^[50] The province continues to order supplementary batches of plates from Waldale. Since 2017, the Ontario die set has been in use. These plates are almost identical to those made by Trilcor Industries. The Waldale made plates have squared off edges and smaller bolt holes.^[51]

Defective plates from 2012

In 2012, reports began to appear of plates deteriorating earlier than otherwise expected. The reflective layers detached themselves from the metal plate, making the plate unreadable. Approximately 1% of licence plates issued have this defect. The defect has appeared in both front and rear plates. Trilcor Industries and the MTO offer a five-year warranty on plates and will replace the defective plates at no cost.^[52] Plate replacement for other reasons (theft, damage, wear, etc.) is done at a cost.

Conventional plates can be replaced "over-the-counter" at a licence office, but the complete process for personalized plates takes over six months.^[53]

Driving with an illegible plate is an offence punishable by fine, under the Highway Traffic Act.^[54]

In 2015, the Ministry of Community Safety and Correctional Services hired Canada's National Research Council to identify the root cause of licence plate de-lamination. The NRC's report indicated that the reflective material adhered poorly to the aluminium plates, and that embossing process stressed the materials to the point that the reflective layer would puncture and de-laminate. At that point, water and other contaminants could slip between the layers. Also, road de-icing materials contributed to the de-lamination. The report found that this problem was present in samples from all types of plates, except for motorcycle plates.

The report recommended that Trilcor work with its supplier of laminating layer to resolve the problem, and indicated that a thicker layer of material would likely perform better.^[55]

• Example of early deterioration of front Ontario Number Plate
• Early deterioration on a rear plate. The aluminum base is visible where the reflective layer has fallen off.
• Close-up view of early damage to a front licence plate of an Ontario car. The reflective layer can be seen de-laminating and separating from the metal base.
• Close-up view of similar damage to the rear plate of the same car, indicating this problem is not confined to the front plates.
• For comparison purposes, corrosion on this plate is due to age and wear, rather than a defective substrate.

Illegality of licence plate covers

Many vehicle owners place clear plastic covers over their licence plates to protect their already defective licence plates (2012) from premature deterioration.^[56] According to Ontario's Highway Traffic Act Section 13.2, licence plate covers are considered an obstruction and are illegal in the province of Ontario.^[57] In the rare event that the officer chooses to issue the citation, the offence carries a minimum fine of $85.^[58] On the contrary, drivers operating a motor vehicle with defective (i.e. unreadable) number plates can be charged with the same offence.^[57] This has left defective number plate owners with little choice but to obtain replacement plates from the MTO, orders which have taken months (or over six months for customised plates) to process.^[56]

Several motorists sought other solutions to prevent their number plates from deterioration, such as placing the front plate on the dashboard instead of affixing it to the front bumper.^[59] Others have omitted the front licence plate altogether since it is not uncommon to see out-of-province vehicles on Ontario roadways (many jurisdictions in North America, including neighbouring Quebec and Michigan, do not require front plates). In most cases, vehicle owners who attempted the aforementioned solutions were convicted of the same offence (HTA section 13.2).^[59]

Defective plates from 2020

On 15 February 2020, two weeks after the province began issuing plates with the new design, off-duty Kingston Police Sergeant Steve Koopman posted a photo on Twitter showing a vehicle with the new plate at night, stating that "they're virtually unreadable at night".^[60] Government spokesperson Lisa Thompson, the Minister of Government and Consumer Services, stated in a news conference that the new design had undergone a "rigorous testing program", that the government had consulted with "key stakeholders" including law enforcement, and that the plates were not problematic.^[60][61] She also criticized the earlier "Liberal plates",^[60] referring to a batch of plates issued during a previous government that peeled. Thompson stated that manufacturing and quality control are the responsibility of 3M.^[61] The redesigned plates also caused problems for photo radar cameras, which have difficulty reading the name of the jurisdiction. The name is rendered in a smaller font size than earlier plates.^[61] The president of the Toronto Police Association stated that the organization had not been consulted on the new design.^[60]

The Ford Government had insisted for days that there was not an issue with the plates; however, on February 20, it announced that 3M would make an "enhanced licence plate" to be available in less than three weeks.^[62] On February 28, the government announced that the distribution of the defective plates would cease on March 4, that the enhanced plates would be ready by March 16 at "no cost to Ontario taxpayers", those who had already been issued the new plates will receive the enhanced version in the mail, and until the enhanced plates were ready, the government switched back to the previous plate design.^[63][64] This design was later scrapped on May 6.^[20]

Sticker renewal fee

On February 22, 2022, the Ford Government eliminated licence plate renewal fees and the requirement to have a licence plate sticker for the nearly eight million passenger vehicles, light-duty trucks, motorcycles and mopeds, effective March 13, 2022.^[65]