Why do British cars never use the letters "I", "Q" or "Z" on their number plates?

Question

Right! I've tried several times to foil you guys out there, but you always get the better of me. Now see if I can beat you with this question.

Why do British cars never use the letters "I", "Q" or "Z" on their number plates? I've heard the explanation that the letter "I" can be confused with the number 1, and that maybe the letter "Q" could possibly be too close to the number 0. However, if that was the reason, they wouldn't use the letter "O" because it is almost the exact replica of the number "0".

Surely I must have got you flumaxed this time?

Answer 1

With the pre-1962 number plate system each plate has two or three letters plus up to four numbers.
The two letters (or 2nd and 3rd of three numbers) represented the place of registration, and these were allocated prior to the foundation of the Republic of Ireland. All combinations containing "I" or "Z" were issued to Ireland.
Northern Ireland still uses this system, with three letters followed by four numbers. Northern Ireland does use "I" for the first of the three letters also, but England, Scotland and Wales never did. "Z" has never been used in the first letter position.
The Republic of Ireland changed to a new system in 1986.
"Q" was never used because it could have been mistaken for an "O". Mistaking an "O" for a zero was never an issue, as there should always be a space between the letters and numbers.

When the annual suffix system was introduced in 1962, the same two-letter place of origin codes as before were retained, and stayed in use until the current system was introduced in 2001.
However, a much reduced list of letters was used for the suffix (or prefix from 1983 to 2001) as the suffix was positioned next to the numbers, hence "O" could have been mistaken for "0" and "I" for "1". "U" or "Z" were not used either, in case they were mistaken for "V" or "2".
"Q" was used, but to represent a vehicle of undetermined age (say a rebuilt car with old mechanicals but a new shell), hence is not common.

With the new system, "I" is never used (probably reserved for future use in Northern Ireland), "Q" is not used so it is not mistaken for an "O" (and the previous system for cars of undetermined age is still in use), and "Z" is not used in the place codes (again may be reserved for Northern Ireland), but is used in the second and third positions in the three-letter "random" part of the number. In fact an example often used for the current system is "AB 51 XYZ". Fewer letters are used in the first position of the three-letter sequence due to the closeness to the numbers. For example "AB 51 OZY" could be mistaken for "ABS 102Y", but "AB 51 XZY" could not be mistaken for any other possible UK number.

Answer 2

Letter I wasn't used because if the possible confusion with the number 1 (though it is in N Ireland.)

A Q prefix means it is a "query" plate, usually because it's a kit car built with bits from many sources or because it's a military vehicle re-registered on the civvy system. Just means there's no certain way of determining age. Otherwise, it's not used in the "body" of the plate because of the potential for confusion with O.

Z wasn't used in GB because of the possible confusion with the number 2 (though it is in N Ireland). It is now, though, because the new way of laying out number plates avoids this confusion.

N Ireland have their own system because they're not part of Great Britain, although they're part of the "United Kingdom of Great Britain and Northern Ireland"

That do you? lol

Answer 3

The letter 'I' can be confused with the number 1, the 'Q' plates are for cars purchased tax free in UK for export and 'Z' was designated for Northern Ireland number plates. As for the letter 'O'..... I don't know.

Answer 4

They were considered too easy to mistake for other letters or numbers and were kept for special circumstances.They used the number "o" because the letter o was not used,so,no confusion.

Answer 5

The alphabet wasn't created specifically for the English language.

Answer 6

"I" could be a 1 or L
Q is used as a "Q plate which means it has been re-built or changed to another vehicle, or Kit car.
"Z" is not used on pre-fixed number plates. but is used from year
2000 onwards. (sorry you could not get a private plate)

Answer 7

I don't think that 'O' is used either.
Q could look like 0 (but is used in Ireland)
and I'm not sure about Z - perhaps there was just no call for it?

Answer 8

Q is used, actually. If the date that a vehicle was first placed in service can't be detemined, it gets a Q. Ditto if it's a rebuilt write-off.

Answer 9

Z could be mistaken for 2

Answer 10

'I' coz it might get mixed up with 'L', 'Q' coz that's used for import cars and 'Z' I'm not sure but possibly coz it can be mistaken for '2' - smack my wrist if its wrong!!