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malevolent design weblog

This blog is now defunct, but you can find more stuff over at my personal site

Telephone Number Usability

To display a UK telephone number to potential callers inside and outside the UK, people often use the format

+[country code] ([trunk prefix])[area code] [local number]
e.g. +44 (0)1234 567890

The trunk prefix is something you only have to dial within the UK (it’s considered part of the area code internally), hence the separation, but this approach is problematic. Do international callers know to omit the 0? It’s particularly confusing as parentheses are generally used around the area code elsewhere. And do UK callers know to either omit the +44 and include the 0, or include the +44 and omit the 0?

I’m not convinced it’s clear and helpful for anyone; something like (+44/0) 1234 567890 would at least try to convey the either/or nature of the information.

Anyway, I’m going to stop using it. I propose the following alternative approaches:

Overwhelmingly UK-based audience
([trunk prefix][area code]) [local number]
e.g. (01234) 567890
Omit parentheses for national/mobile numbers
Truly international (no strong UK bias)
+[country code] [area code] [local number]
e.g. +44 1234 567890
Mixed (perhaps mainly UK but significant international element)
Both of the above, clearly labelled
e.g. UK Tel.: (01234) 567890, International: +44 1234 567890

For business-to-business or a tech-savvy audience you can get away with using just the international format slightly more often (people are increasingly putting all numbers into their mobiles and computers in international format so they’ll work when travelling or using VoIP).

Does anyone know where the (0) approach comes from? Like so many things, it’s firmly established but doesn’t make sense once you stop and think.


Or you can use the approach that some scammers have tried on the car sales site I'm working on.

They can advertise their car for only £4.95 until it is sold. What they do is put an expensive car up for sale at £5,000 less than it should be -with an 070... number as their contact number.

These are the geographically 'independent' numbers, which basically cost from 35p a minute to well over 50p a minute to call.

Also, there are people who email those selling cars, saying that they are interested, and ask the seller to call them on 070...

These numbers look too much like mobile phone numbers - and they really aren't required. Although I'm not sure what the scammers would do if they were abolished.

Daniel, 13th Oct, 4:24pm

The super-geniuses at Ofcom have finally realised that keeping 07 mobiles-only would be sensible, so 'personal numbering' will probably be shifted to 06 next year.…

Matt Round, 13th Oct, 5:55pm

Possibly, rather than probably...

Daniel, 13th Oct, 6:48pm

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