Quick answer: In the UK, Australia, and most Commonwealth countries, the correct spelling is instalments (with one ‘l’). Installments (with two ‘l’s) is the standard American English spelling. If you are writing for a British audience, always use instalments.
It is one of the most persistent headaches for editors and writers working across international borders. You draft a contract, a blog post, or an email, and suddenly you are staring at a red squiggly line under a word that looks perfectly fine to your eyes. Is it installments or instalments? The confusion stems from the divergent evolution of British and American English spelling conventions, specifically regarding the doubling of consonants in suffixes. For anyone targeting a UK readership, getting this right is not just about aesthetics; it is about credibility and adherence to local standards.
| Term | Meaning / When to use | Example sentence |
|---|---|---|
| Instalments | Correct UK/Commonwealth spelling. Use when writing for audiences in the UK, Australia, New Zealand, or Canada (though Canadian usage can vary). | “The loan will be repaid in monthly instalments over five years.” |
| Installments | Correct US spelling. Use only when writing for an American audience or adhering to US style guides (like AP or Chicago). | “The software subscription is billed in quarterly installments.” |
When to use instalments
If your primary audience is in the United Kingdom, you must use instalments. This follows the standard British English rule where the final consonant of a root word is often not doubled when adding a suffix if the stress does not fall on the final syllable, or due to historical simplification trends championed by lexicographers like Noah Webster’s counterparts in Britain who retained older French-influenced spellings. Actually, in this specific case, it is the Americans who doubled the ‘l’, while the British kept the single ‘l’ from the original French acompte or Latin roots, though the etymology is complex. The key takeaway for the modern writer is simple: UK = single ‘l’.
I see this error constantly in financial documents and e-commerce checkout flows designed for British customers. Using the American spelling can make a brand look foreign or careless. Here are three concrete examples of how to use it correctly in a UK context:
- In a formal business email: “Please confirm that you agree to pay the outstanding balance in three equal instalments by the end of the quarter.”
- On a retail website footer: “Buy now, pay later with interest-free instalments available at checkout.”
- In a legal contract clause: “The Tenant shall pay the Rent in monthly instalments on the first day of each month.”
the concept of paying in parts is formally known as an Instalment in many jurisdictions outside the US, reinforcing the single-‘l’ preference in international legal and commercial contexts that lean towards British English norms.
When to use installments
You should use installments only when you are writing for an American audience. This includes clients based in the US, publications that follow American style guides (such as the Associated Press Stylebook or the Chicago Manual of Style), or global brands that have adopted US English as their corporate standard.
American English often doubles the final consonant when adding a suffix to a verb ending in a vowel + consonant, even if the stress isn’t on the final syllable, although install is a bit of a special case where the doubling was standardized early in American lexicography. The result is a double ‘l’. If you are submitting an article to a US-based magazine or writing copy for a Silicon Valley startup, installments is the required form.
Here is how it looks in practice for US-focused content:
- In a SaaS pricing page: “Choose our annual plan and save 20% compared to monthly installments.”
- In a news report: “The car was purchased via a financing plan with low-interest installments.”
- In a personal finance blog: “Many Americans struggle to keep up with their credit card installments during inflationary periods.”
It is worth noting that the term itself refers to a part of a debt or payment that is paid at regular intervals. As detailed in the entry for Installment sale, this financial structure is prevalent in the US market, where the double-‘l’ spelling is universally recognized and expected.
How to remember the difference
Memory tricks are essential for writers who switch between dialects frequently. Here is the most effective mnemonic I use in my editing workshops:
“The UK keeps it minimal; the US adds more.”
Think of the single ‘l’ in instalments as being “minimalist,” which fits the stereotype of British reserve or efficiency. The double ‘l’ in installments is “more,” reflecting the American tendency in spelling to emphasize phonetic clarity or simply follow different historical standardization paths.
Another trick involves geography:
- UK has 4 letters in its abbreviation (if you count U-K as two, but think of “Britain” vs “America”). Let’s try a better one:
- London has one ‘n’ in the middle? No, that’s confusing.
- Try this: US has two letters, so it uses two Ls. UK has two letters too, so that doesn’t work.
Let’s stick to the visual cue:
- Installments (US): Think of LL as looking like two parallel lines, like the stripes on the US flag or the rails of a railroad (a very American symbol).
- Instalments (UK): Think of the single L as a lone pillar, like a stone column in a historic British building.
Or, simpler still:
- America = Add an extra L.
- Britain = Basic (single) L.
Common mistakes and exceptions
Even experienced writers stumble when dealing with mixed audiences or automated tools. Here are the most common pitfalls and how to avoid them.
1. Spellchecker Settings
Your word processor’s default dictionary dictates what it marks as an error. If your Microsoft Word or Google Docs is set to “English (United States),” it will flag instalments as incorrect. Conversely, if it is set to “English (United Kingdom),” it will flag installments. Always check your document settings before finalizing a piece. I once edited a 50-page white paper where the author had manually “corrected” the UK spelling to US spelling because their spellchecker was insisting on it, ruining the consistency for their London-based client.
2. Canadian Ambiguity
Canadian English is a hybrid. It often follows British spelling for words like colour and centre, but can be inconsistent with others. However, for instalments, Canadian government and legal documents typically prefer the British instalments. But be careful: some Canadian media outlets may use the American installments due to proximity and influence. If writing for Canada, check the specific style guide of the publisher. If none exists, instalments is generally safer and more traditional.
3. Brand Names and Proper Nouns
Never “correct” a brand name. If a US company calls their service “Klarna Installments” in their official marketing materials, you must use their spelling, even if you are writing for a UK blog. However, in generic descriptive text surrounding that brand, you should revert to the local spelling.
- Incorrect: “You can pay using Klarna Instalments.” (If the brand uses double L).
- Correct: “You can pay using Klarna Installments, which allows you to split costs into manageable instalments.”
4. Derivatives
The rule applies to related words too.
- UK: Instalment plan, instalment book.
- US: Installment plan, installment book.
Do not mix them within the same document. Consistency is key. If you start with instalments, do not switch to installments halfway through.
Frequently Asked Questions
Is “instalments” correct in American English? No, instalments is considered a misspelling in American English. The standard US spelling is always installments with two ‘l’s.
Can I use “installments” in the UK? While readers will understand you, using installments in the UK is marked as non-standard and may appear unprofessional or Americanized. It is best to stick to instalments for UK audiences.
What about other words like “traveller” or “labelled”? This follows the same pattern. UK English doubles the ‘l’ in traveller and labelled (because the stress is on the first syllable but the ‘l’ is doubled in UK convention for these specific roots), whereas US English uses traveler and labeled. Wait, actually, install is unique because the stress is on the second syllable (in-STALL), yet US doubles it and UK doesn’t. For travel, UK doubles it (traveller) and US doesn’t (traveler). So the rule isn’t perfectly uniform across all words, but for instalment/installment, the UK/US split is strictly single/double ‘l’.
Does Apple or Microsoft use one spelling over the other? Both companies localize their content. If you are using an iPhone set to UK English, Siri and system texts will use instalments. If set to US English, they will use installments. Always match the spelling to the locale setting of your target user base.
Samantha Jones graduated with a Bachelor’s degree in English Literature from Oxford University and has been involved in language education for over 15 years. Her expertise lies in comparative language analysis, focusing particularly on the differences and similarities in spelling across various English dialects. Samantha’s passion for this niche developed from her love of storytelling and desire to preserve the subtle differences that make English unique around the globe. On SpellRightDaily, she crafts detailed articles that compare common spelling errors and offer practical advice for writers and editors looking to polish their work. Samantha’s content is known for its clarity and depth, helping readers decode complex spelling issues and improve their writing skills. She also enjoys delving into the psychology of language learning, and how cognitive factors influence the retention of correct spelling patterns. Her engaging writing encourages a deeper appreciation of the language’s rich diversity.