UK vs US English: a (fairly) comprehensive checklist

Swapping between US and UK English can be a minefield. Use this handy proofing checklist to avoid the most common regional mix-ups.

uk us

Have you ever heard the name ‘Nicole Mowbray’? In the early 2000s, Nicole caused an international incident – all because of a simple mishap involving British and American English.

Flashback to 2003. George Bush is heading into his third year as president (a relevant fact, I promise). And Nicole has just started her first job as a journalist at The Observer.

One night, Nicole is presented with an email to type up. The only instruction she is given: ‘don’t make any mistakes’, so she carefully types it up. The next morning, the memo is splashed across the front page, with the headline: “Revealed: US dirty tricks to win vote on Iraq war”.

Unfortunately, her work then begins to gain attention for all the wrong reasons. The story in question concerned a US memo leaked by British whistle-blower Katherine Gun – but when Nicole typed it up, she translated the American writing into British English. As a result, the entire story is thrown into doubt, with hordes of readers claiming the memo is fake and the whole incident was a hoax.

Fast-forward to now, and this mishap is near forgotten. But Nicole’s lesson is an important one to learn – even for B2B marketers. Especially for B2B marketers. Although it’s unlikely that mistaking ‘ize’ for ‘ise’ will cause an international incident, even the smallest mistranslation can distract from the story you’re trying to tell.

And for marketers with an international client base, you’ll find yourself switching between them pretty frequently. So, we’ve put together a handy checklist to help.

Make sure you’re using the right spelling

Some of the biggest – and smallest – differences between US and UK English are spellings. Here are the ones most likely to catch you out:

  1. -ise/yse to –ize/yze

As a B2B copywriter or marketer, the most common examples you’ll come across are: realise, analyse, maximise and virtualise. Or, for American English, realize, analyze, maximize, virtualize (and so on).

This also applies to organisation and organization.

  1. -l to –ll

Adding a suffix to a word – especially if the suffix begins with a vowel – can require doubling the final consonant. But UK English and US have their own rules, sometimes requiring double consonants, and sometimes not. So (after some surprisingly extensive research by yours truly) here’s a quick guide to the rules of doubling up.

In UK English, if a word ends -l, the consonants are usually doubled up, whether the final syllable is stressed or not. For example, cancel becomes cancelled, travel becomes travelled, and fuel becomes fuelled.

In US English, the consonants are only doubled if the second syllable is stressed. So control becomes controlled, and model becomes modelled. But cancel becomes canceled, travel becomes traveled and fuel becomes fueled.

And if this wasn’t confusing enough, there are a few exceptions:

  • Parallel always becomes paralleled (imagine the mouthful it would be otherwise).
  • In UK English, there are a few words where the root spelling is different. For example, it’s enrol and fulfil, rather than enroll and fulfill. When adding a vowel suffix like -ed, the consonants are doubled, creating ‘enrolled’. When adding -ment, however, they’re not – it’s ‘enrolment’. (And in US English, it’s always -ll, so it’s enrollment.)
  1. our to -or

This one’s a lot simpler to remember – but can still be easy to miss. Where we Brits have added a somewhat unnecessary ‘u’, American English removes it. Behaviour, colour, neighbour, humour, and labour all become behavior, color, neighbor, humor and labor.

  1. -re to –er

When you’re writing for B2B tech companies, the words ‘data centre’ will almost certainly come up at some point. Except, in US English, it’s ‘data center’ – an easy mistake to make, and an easier one to skip while proofreading. The same goes for theatre, fibre and litre, although you might not be using these words quite as frequently.

  1. -ence to -ense

If you drive without a licence in the UK, you could be committing an offence with no defence. In the US, however, the only defense to your offense would be having a permit. Make sense?

  1. And a few more…

There are many small differences between US and UK spelling. We’ve laid out the ones most likely to catch you out if you’re writing for a business audience, but here are a few more to keep your eyes peeled for:


Encyclopaedia Encyclopedia
Learnt, earnt Learned, earned
Sizeable, likeable Sizable, likable
Orientated Oriented
Tonne Ton
Mould Mold
Catalogue, dialogue Catalog, dialog
Manoeuvre Maneuver
Forwards, towards Forward, toward
Instil, skilful, instalment Instill, skillful, installment
Aeroplane Airplane
Grey Gray
Cheque, current account Check, checking account
Judgement Judgment


Nail your punctuation

Sadly, the variation between British and American English doesn’t stop at spelling. Each have their punctuation quirks, too. However, while this blog aims to provide a quick checklist, these aren’t hard and fast rules and uses will vary between companies. So referring to a company style guide is always your best bet.

  1. Oxford comma

In American English, an Oxford (or serial) comma is usually mandatory if you’re listing three things or more. In UK English, it’s only used when a sentence is unclear without it. Ironic really, when the comma is named after a UK university, but who are we to judge? For a more detailed guide to the oxford comma, check out this supremely helpful blog by my colleague Ben.

  1. The dash

Since I’ve started working at Radix, using en dashes ( – ) and em dashes (—) correctly has plagued me. Once, in brighter times, I was unaware of their existence. Now, I spend hours scouring my finished work, checking I’ve used the little bastards correctly. (Well, maybe not hours, but definitely an alarming length of time.)

Personal feelings aside, the general rule is this: en dashes with spaces are preferred in UK English style guides, em dashes without spaces are more common in style guides that use US English.

But, as with every bit of grammar, there are exceptions. En dashes, not em dashes, should be used to indicate spans of time or number ranges. For example, between 2019–2020, I spent 5–8 hours a day proofing my dash usage.

And, god forbid, never use a hyphen by mistake.

  1. Titles

In UK English, you don’t put full stops after a title – for example, it’s Mrs Doubtfire and Dr Jill Biden. But if you’re swapping to US English, you’ll need to add a full stop in, and write about Mrs. Doubtfire and Dr. Jill Biden.

  1. Quotation marks

When you’re using quotation marks in US and UK English, you’ll need to follow different rules.

In UK English, single quotation marks are used for the initial quote. Then, for single quotes, double quotation marks are needed. For example:

‘We’ve embraced digital transformation’, says CEO Alex Smith. ‘And now, we can provide our customers with faster, better services. The results have been “nothing short of staggering”, according to one happy customer.’

In US English, it’s just the other way around:

“We’ve embraced digital transformation,” says CEO Alex Smith. “And now, we can provide our customers with faster, better services. The results have been ‘nothing short of staggering,’ according to one happy customer.”

  1. Date and time

This one might seem obvious, but it’s caught me out once or twice so it’s always worth double checking. American dates follow a month/day/year format, while British dates go day/month/year.

  1. Collective nouns

Knowing when to use ‘is’ and ‘are’ can be complicated, especially when you’re swapping between UK and US English. As a general rule, collective nouns are thought of as singular in American English, and plural in British. For example:

In the UK, your audience are using social media channels.

In the US, your audience is using social media channels.

Check your slang, aphorisms and imagery

Finally, you’ll need to make sure you haven’t included any phrases that are specific to the UK or America. This could include a colloquialism or turn of phrase that is specific to a certain country, your vocabulary choice, or using £ instead of $ (or vice versa).

To ‘ace’ something is inherently American (although if something is ace – as in really cool – that’s very British), as is the word ‘awesome’, and the phrase ‘kick it to the curb’. Meanwhile, ‘bog-standard’ is a British phrase, as is ‘spanner in the works’. And there are many, many more, so it’s worth keeping in mind when you’re proofreading.

Similarly, across American and British English, there are some words that are just different. Some you’ll know (gas/fuel, parking lot/car park etc), but others could catch you out (anticlockwise/counter-clockwise, for example). If you want a concise list, here’s a good place to start.

Anything to add?

When you’re swapping between UK and US English on a regular basis, making a few mistakes along the way is inevitable. Perhaps you have your own pet peeves, or phrases that have you reaching for the ctrl+f key every time.

We’d love to hear them – or anything that we’ve missed in this checklist. Tweet us at @radixcom, or pop us an email at

Lizzie Cresswell

When you need short-form content that’s snappy, informed, and understands its audience to a tee – you can count on Lizzie to deliver. And as a perfectionist with a keen eye for detail, she’s quickly become one of our most trusted proof-readers. When she’s not writing another winning ABM campaign, you’ll likely find her trekking the Cornish coast.

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