10 Grammar Mistakes That Are Killing Your Business Emails

Published: 2026-06-16 · 8 min read

I've reviewed something like 3,000 business emails in the last two years — client proposals, internal memos, cold outreach, executive summaries, you name it. And the same mistakes show up over and over, regardless of industry or seniority level. A VP at a Fortune 500 company makes the same "your vs you're" slip as an intern. The difference is the VP's mistake costs credibility.

Here's the thing about email grammar: nobody will call you out on it. They'll just silently adjust their impression of you downward. A 2023 Grammarly study of 500 hiring managers found that 67% said a single grammar error in a candidate's email would negatively affect their perception — and 41% said it would count against the candidate in a hiring decision. For client-facing roles, those numbers were even higher.

Below are the 10 mistakes I see most often, each with the actual broken sentence and the fix. None of these take more than 30 seconds to correct.

1. Your vs. You're

Why it's fatal: This is the most basic distinction in English. Getting it wrong signals either you don't know the rule or you don't care enough to proofread. Neither is a good look.

The fix: Expand "you're" to "you are" in your head. If the sentence still makes sense, use the apostrophe. If it doesn't, use "your." This takes literally one second.

2. Its vs. It's

Why it's fatal: Same category as your/you're. The difference is this one slips through spellcheck because both are valid words.

The fix: Same trick as your/you're. Expand to "it is." Works? Apostrophe. Doesn't work? No apostrophe.

3. Comma Splices

Why it's fatal: A comma splice makes your writing feel rushed and amateurish. It's two complete sentences jammed together with nothing but a comma between them, and it's probably the single most common error in professional email.

The fix: Three options. Replace the comma with a period (two separate sentences). Replace it with a semicolon. Or add a conjunction (and, but, so) after the comma. Any of the three works. The one thing that doesn't work is leaving it as a bare comma.

4. Subject-Verb Agreement (When The Subject Is Buried)

Why it's fatal: This one is insidious because it usually happens in longer sentences where the subject and verb are far apart. The writer loses track of what the subject actually is.

The fix: Strip the sentence down to its skeleton. "The quality... were inconsistent" or "The quality... was inconsistent"? The subject is "quality" (singular), so the verb must be "was." Ignore the prepositional phrases in between — "of the reports," "submitted last quarter" — they're decoration, not the subject.

5. Me vs. I (In Compound Objects)

Why it's fatal: People overcorrect. They got yelled at for saying "Me and John went to the meeting" in third grade, so now they say "Please send the report to John and I" — which is also wrong, just in the opposite direction.

The fix: Remove the other person from the sentence and see what sounds right. "Please loop in I"? No. "Please loop in me"? Yes. So it's "Sarah and me." This trick works every single time.

6. Dangling Modifiers

Why it's fatal: These can actually change the meaning of your sentence into something you didn't intend — sometimes something absurd. A dangling modifier attaches to the wrong noun, and the result is confusing at best, comically wrong at worst.

The fix: After an introductory phrase, the very next word should be whoever or whatever is doing the action. If "After reviewing the data" starts the sentence, the next word better be the person who reviewed the data (I, we, the team).

7. Then vs. Than

Why it's fatal: These aren't typos — they're different words. Using "then" when you mean "than" (or vice versa) makes you look like you never learned the distinction.

The fix: Than = comparison (better than, faster than, more than). Then = time or sequence (first this, then that). If you're comparing things, it's "than" with an A. If you're ordering events, it's "then" with an E.

8. Missing Commas After Introductory Phrases

Why it's fatal: This one flies under the radar because the sentence is technically still readable without the comma. But its absence creates a breathless, run-on quality that makes your writing feel unpolished.

The fix: If your sentence starts with a phrase that sets up context — time, location, condition — put a comma between that phrase and the main clause. Read it aloud. If you naturally pause after the introductory phrase, you need a comma there.

9. Apostrophe Errors in Plural vs. Possessive

Why it's fatal: Throwing an apostrophe into a plain plural is sometimes called the "grocer's apostrophe" (banana's $2, apple's $3). In emails, it makes you look careless with basic mechanics.

The fix: Ask yourself: does something belong to this word? If yes, apostrophe. If it's just more than one of something, no apostrophe. "Reports" (multiple reports, no apostrophe) vs. "the report's cover page" (the cover page belonging to the report, apostrophe).

10. Vague Pronoun References

Why it's fatal: This is the silent killer. The sentence is grammatically correct, but nobody knows what "it" or "this" or "that" refers to. In business communication, ambiguity creates confusion, and confusion creates delays.

The fix: Every time you write "it," "this," "that," or "they," stop and ask: would a colleague who knows nothing about this situation know exactly what I'm referring to? If there's any doubt, replace the pronoun with the actual noun.

The 30-Second Pre-Send Checklist

I don't expect anyone to memorize all 10 items. Here's what I actually do before hitting send on anything important:

1. Your/You're check: Expand "you're" to "you are" mentally. Right or wrong? Fix if needed. (5 seconds)
2. Its/It's check: Same trick with "it is." (5 seconds)
3. Read the first three words of every sentence aloud in your head. If it starts with "Before we proceed I'd like..." you're missing a comma. (10 seconds)
4. Scan for semicolons you didn't mean to write. If there's a semicolon anywhere, verify both sides are complete sentences. (5 seconds)
5. Check every "than" and "then." Is it a comparison? If so, "than." (5 seconds)

That's 30 seconds. It catches probably 80% of the errors on this list. For the remaining 20% — the subject-verb agreement issues, the dangling modifiers, the sneaky stuff — I run important emails through grammaraicheck.com before sending. It catches things my eyes skip over, especially when I've read the same paragraph five times and my brain has stopped registering the words.

One Last Thing

I want to be clear about something: making grammar mistakes doesn't mean you're bad at your job. Some of the smartest people I've worked with can't spell "accommodate" without looking it up. What matters is whether you catch the mistakes before someone else does. A clean email says "I paid attention." A sloppy one says "I didn't have time to proofread" — even if you spent two hours writing it.

The difference between the two is usually about 30 seconds of checking.

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Frequently Asked Questions

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