Choosing between amortize and amortise can be confusing, especially when writing about loans, mortgages, accounting, or financial planning. Both spellings are correct, but the preferred version depends on the type of English you use.
Amortize is the standard spelling in American English, while amortise is commonly used in British English and other varieties that follow British spelling conventions.
Although the spelling changes, the meaning remains the same: to gradually pay off a debt or spread a cost over a specific period. In this guide, you will learn the difference, discover practical examples, and understand which spelling suits your audience.
Key Takeaways
- Amortize is the American English spelling; amortise is the British English spelling.
- The word has two finance meanings: paying off a loan gradually, and spreading a cost over time.
- The noun follows the same pattern: amortization (US) and amortisation (UK).
- Whichever form you choose, use it consistently through the whole document.
What Does “Amortize” Mean?
To amortize is to deal with a debt or a cost gradually, in set amounts over a period of time, instead of all at once. It is a finance and accounting word, and it works in two related ways.
Amortizing a loan or mortgage
When you amortize a loan, you pay it off with regular payments — usually monthly — that cover both interest and part of the amount you borrowed, called the principal. Early payments are mostly interest. Later payments are mostly principal. By the final payment, the debt is gone.
Lenders show this plan in an amortization schedule: a table listing every payment, how much goes to interest, how much goes to principal, and the balance left after each one. Most home mortgages work exactly this way.
Amortizing a cost in accounting
In accounting, to amortize a cost means to spread it out over the years the thing is useful, rather than recording it all in one year. Accountants amortize intangible assets — things you cannot touch, like patents, copyrights, and trademarks. A patent that cost $10,000 and lasts ten years might be amortized at $1,000 a year.
Physical things like machines and vehicles are handled the same way but with a different word: depreciate. More on that below, because mixing the two up is a classic mistake.
A word that means “to kill off” a debt
Amortize has a surprisingly dark history. It comes from Old French amortir, “to deaden or kill,” built from Latin mors, meaning death. To amortize a debt, in the oldest sense, is to kill it off — payment by payment, until it is dead.
Amortize vs. Amortise: The Only Difference Is One Letter
Here is the honest truth: there is nothing to choose between the two words except spelling.
| Amortize | Amortise | |
|---|---|---|
| Used in | United States | United Kingdom |
| Ending | -ize | -ise |
| Meaning | Pay off gradually / spread a cost | Pay off gradually / spread a cost |
| Example | They amortized the loan. | They amortised the loan. |
Amortise is not a misspelling, and amortize is not a typo either. Dictionaries list amortize as the main form and amortise as the British variant — Collins notes that in British English you “also use amortise,” Cambridge marks it “UK also amortise,” and Dictionary.com labels amortise “especially British.”
Which Spelling Should You Use?
Use the spelling your readers expect. That one rule settles almost every case.
Writing for an American audience
Use amortize. It is the form in Merriam-Webster, the form in US bank and mortgage documents, and the form American style guides expect. An American reader in finance may flag amortise as a typo, even though it is a real word.
Writing for a British audience
Use amortise for general readers — it is the everyday British choice, and you will see “amortised” throughout UK company accounts and textbooks. But amortize is not wrong in Britain. Oxford spelling keeps the -ize ending, and British financial publishers use both, so the z form causes no confusion there.
Writing about finance or accounting
Match the document, not just the country. US loan paperwork, SEC filings, and American accounting standards use amortize and amortization without exception. UK annual reports usually use amortise and amortisation. If a document already uses one form, follow it.
Why does English have two spellings?
The -ize ending comes from the Greek ending -izein, carried into Latin as -izare. French later softened the ending to -iser, and British English picked up that French-style -ise. American spelling kept -ize. Amortize is a special case: the word entered English from French centuries ago, and the -ize spelling later took over — one reason both forms feel natural today.
Whatever you pick, pick it once. Writing “amortize the loan” in one paragraph and “the amortisation schedule” in the next looks careless. Set your spellchecker to US English or UK English and let it police the choice for you.
Every Word Form: Amortize and Amortise Side by Side
The s/z swap runs through every form of the word, including the noun — which matters here, because “amortization schedule” is such a common phrase.
| Form | American English | British English |
|---|---|---|
| Base verb | amortize | amortise |
| Third person | amortizes | amortises |
| Past tense | amortized | amortised |
| -ing form | amortizing | amortising |
| Noun (process) | amortization | amortisation |
| Adjective | amortizable | amortisable |
British writers also use “amortization” very widely — Cambridge lists amortisation simply as the UK alternative — so the noun is forgiving. Your verb choice should still match your audience.
Examples in Sentences
American spelling (amortize):
- The couple amortized their mortgage over thirty years.
- The company will amortize the cost of the software over five years.
- Each month, the schedule shows more of your payment going to principal.
British spelling (amortise):
- The loan was amortised over the life of the mortgage.
- The firm amortises the patent over ten years.
- Business expenses had to be amortised over a 60-month period.
Both sets of sentences are correct. What would be wrong is mixing them — “she amortised the loan” in one sentence and “the amortization table” in the next. Together they clash; apart, each is fine.
Common Mistakes to Avoid
- Treating amortise as a typo. It is standard British spelling, listed in every major dictionary.
- Confusing amortize with depreciate. You amortize intangible assets (patents, copyrights) and loans. You depreciate physical assets (machines, vehicles, buildings). Same idea, different word.
- Mixing the noun with the wrong verb. Amortize goes with amortization; amortise goes with amortisation. Do not pair them across.
- Thinking amortize only works for mortgages. Loans are the famous case, but the accounting sense — spreading any qualifying cost over time — is just as common in business writing.
- Using amortize for a one-time payment. If the whole amount is paid at once, nothing is being amortized. The word always means a gradual process.
The 10-Second Rule
If your audience is American, write amortize. If your audience is British, write amortise. Then carry that same choice into the noun: amortization or amortisation. That is genuinely all there is to it.
Frequently Asked Questions
Is amortise or amortize correct?
Both are correct. Amortize with a z is the standard spelling in American English, and amortise with an s is the standard spelling in British English. Neither is a mistake — choose the one that matches your audience.
What is an amortization schedule?
It is a table that maps out a loan from start to finish. For every payment it shows how much goes to interest, how much goes to principal, and how much of the loan is left.
What is the difference between amortize and depreciate?
Both spread a cost over time. The difference is what kind of asset is involved: amortization applies to loans and intangible assets like patents, while depreciation applies to physical assets like machines and vehicles.
What is the past tense — amortised or amortized?
It follows your base spelling. American writers use “amortized,” as in “the loan was amortized over 30 years.” British writers use “amortised,” as in “the loan was amortised over 30 years.”
How do you pronounce amortize?
American English accepts two pronunciations: AM-er-tize and uh-MOR-tize. British English uses uh-MOR-tize. All of them are correct, and the s spelling sounds exactly the same as the z spelling.
Is the noun spelled amortization or amortisation?
Both exist and they follow the same regional pattern: amortization in American English, amortisation in British English. British writers also use amortization widely, so it is the safer noun if your audience is mixed.
Conclusion
In the comparison of amortize vs amortise, the main difference is regional spelling, not meaning. Amortize is preferred in American English, while amortise is widely used in British English.
Both words describe gradually paying off a loan or allocating a cost over time. For example, American financial documents typically use “amortize a loan,” while British publications may use “amortise a loan.” Neither spelling is inherently wrong, so your choice should depend on your audience and the style guide you follow.
Remember to stay consistent throughout your writing, especially in financial reports, business documents, and educational content.
