Grammar Mistakes That Make You Look Unprofessional (Free Tool Included)

7 Grammar Mistakes That Make You Look Unprofessional | Free Grammar Checker

📅 Published: May 5, 2026 | ✍️ By Emma Watson | ⏱️ 6 min read

You have great ideas. You know your industry. Your product or service is excellent. But if your writing is full of grammar mistakes, people will judge you — consciously or not.

In fact, studies show that 59% of people would not use a business that had obvious grammatical errors on their website. That’s lost customers over a missing comma.

Here are 7 of the most common grammar mistakes, how to fix them, and a free tool to catch them before you publish.

Mistake #1: Your vs You’re

❌ Wrong: “Your going to love our new product.”
✅ Correct: “You’re going to love our new product.”

Rule: “You’re” is a contraction of “you are.” “Your” shows possession. If you can replace it with “you are,” use “you’re.”

Mistake #2: Its vs It’s

❌ Wrong: “The company released it’s annual report.”
✅ Correct: “The company released its annual report.”

Rule: “It’s” means “it is” or “it has.” “Its” (no apostrophe) shows possession. This trips up even experienced writers.

Mistake #3: There, Their, and They’re

❌ Wrong: “Their going to bring there laptops over their.”
✅ Correct: “They’re going to bring their laptops over there.”

Rule: “There” = location. “Their” = possession. “They’re” = “they are.”

Mistake #4: Comma Splices

❌ Wrong: “I love writing, it’s my favorite thing to do.”
✅ Correct: “I love writing. It’s my favorite thing to do.”
Or: “I love writing because it’s my favorite thing to do.”

Rule: A comma isn’t strong enough to join two complete sentences. Use a period, semicolon, or conjunction instead.

Mistake #5: Subject-Verb Agreement

❌ Wrong: “The team of writers are working hard.”
✅ Correct: “The team of writers is working hard.”

Rule: The subject is “team” (singular), not “writers” (plural). Singular subjects need singular verbs.

Mistake #6: Who vs Whom

❌ Wrong: “Who did you invite to the meeting?”
✅ Correct: “Whom did you invite to the meeting?”

Rule: Use “who” when referring to the subject of a sentence, “whom” when referring to the object. If you can replace it with “he/she/they,” use “who.” If you can replace it with “him/her/them,” use “whom.”

(Honestly? Most people get this wrong, and conversational English is moving away from “whom.” But in formal writing, it still matters.)

Mistake #7: Misplaced Apostrophes

❌ Wrong: “The 1990’s were a great decade.” or “All employee’s must attend.”
✅ Correct: “The 1990s were a great decade.” “All employees must attend.”

Rule: Apostrophes show possession (the employee’s desk) or contraction (it’s, don’t). They NEVER make a word plural.

Bonus: Frequently Confused Words

  • Affect vs Effect: Affect is usually a verb (to influence). Effect is usually a noun (the result).
  • Lose vs Loose: Lose = misplace. Loose = not tight.
  • Then vs Than: Then = time. Than = comparison.
  • Less vs Fewer: Less for uncountable (less water). Fewer for countable (fewer apples).

How to Catch These Mistakes Before You Publish

Even professional writers make typos. That’s why editing is essential — and why tools like our Grammar & Clarity Checker exist.

Here’s my recommended workflow:

  1. Write your first draft (don’t worry about perfection).
  2. Run your text through our free Grammar Checker to catch common errors.
  3. Read your text aloud — your ears catch what your eyes miss.
  4. Ask a colleague to review if possible.
  5. Use our Paraphrasing Assistant if a sentence feels awkward.
✨ Try it now: Our free Grammar & Clarity Checker instantly finds and fixes common grammar mistakes. Paste your text and see suggestions in seconds.

Final Thoughts

Grammar mistakes don’t mean you’re a bad writer. They mean you’re human. But in business, first impressions matter. A clean, professional email or website page builds trust.

The good news: you don’t need to become a grammar expert. You just need a system. Write, check with our tool, review, and publish. That simple workflow will put you ahead of 80% of competitors.

Now go fix that dangling modifier. Your readers will thank you.

About the Author: Emma Watson is a copy editor and writing coach. She’s helped over 200 businesses improve their content quality.

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