The choice between years, year's, and years' is one of the most searched apostrophe questions in business writing, and for good reason. The three forms look almost identical, but they do different jobs. Get it wrong in a contract, a proposal, or a performance review, and the meaning shifts in ways that can cause real confusion. This guide sorts them out, cleanly.
The plain plural: years (no apostrophe)
When you're simply talking about more than one year, you don't need an apostrophe at all. The word is just years.
- "The project ran for three years."
- "She has fifteen years of experience."
- "The contract expires in two years."
This is the form most writers use correctly without thinking about it. The confusion starts when possession enters the picture.
The singular possessive: year's
Use year's (apostrophe before the s) when one year owns or is associated with something. The apostrophe signals a relationship between the year and a noun.
Common examples you'll see in business writing:
- "This year's budget is tighter than last year's."
- "A year's salary is the standard severance here."
- "One year's notice is required under the terms."
Notice the pattern: you could rephrase each sentence as "the budget of this year" or "the salary of one year." That rephrasing trick is a reliable test. If "of [the year]" works, you need an apostrophe.
The plural possessive: years'
Years' (apostrophe after the s) is for when multiple years collectively own or relate to something. It's the form writers miss most often.
Examples in practice:
- "After twenty years' service, she received a lifetime award."
- "Two years' worth of data was lost in the migration."
- "He has thirty years' experience in supply chain management."
Read those again. In each case, more than one year possesses something (service, worth, experience). The apostrophe still marks possession, but it moves to after the s because the noun is already plural.
The test that always works
When you're unsure, run this two-step check.
Step 1: Is there only one year involved, or more than one? If one year owns something, use year's. If multiple years own something, use years'.
Step 2: Does any year own anything at all? If not, drop the apostrophe entirely and use the plain plural years.
That's the whole framework. Two questions, three possible answers.
Tricky cases worth knowing
A few phrases cause disproportionate trouble in professional documents.
"X years' experience" vs "X years of experience." Both are correct. "Five years' experience" and "five years of experience" mean exactly the same thing. Style guides differ on preference, but neither form is wrong. In a resume or LinkedIn summary, "five years' experience" is slightly more concise.
"In five years' time." Always use the apostrophe here. Five years possess the time, so it's the plural possessive. Writing "in five years time" is the error you'll see most in business emails.
"A hundred years old." No apostrophe. The years aren't possessing anything; you're simply describing an age with a plain adjective phrase.
"20 years' worth." The apostrophe is needed. Worth is the thing being possessed by those 20 years. This pattern comes up often in financial writing and project reports.
Why this matters in business documents
Apostrophe errors are easy to overlook in conversation. They matter far more in written documents. A contract specifying "two years notice" is technically ambiguous, even if the intent is clear to both parties. A proposal claiming "20 years experience" signals to careful readers that proofreading wasn't thorough. Small errors carry outsized weight when a reader is deciding whether to trust a document or its author.
Punctuation choices are as much a signal as a grammar rule. Just as choosing between 9 AM or 9 a.m. says something about your attention to formatting standards, getting year's and years' right marks you as a writer who thinks through details.
Quick-reference summary
Three forms, three jobs:
- years: plain plural, no possession ("three years of work")
- year's: one year possesses something ("a year's salary")
- years': multiple years possess something ("five years' experience")
Run the two-step test on anything that trips you up. One year or many? Does it possess something? The answer to those two questions points directly to the right form.