Common Grammar Mistakes in Professional Writing

Professional documents represent an organization, so clear and correct writing matters. Grammar mistakes can distract readers, create confusion, and make an otherwise polished document appear unfinished.

Some errors are easy to spot, while others are common enough that they can slip through multiple rounds of review.

Understanding the grammar mistakes that frequently appear in professional writing can help you create clearer, more consistent documents.

Subject-Verb Agreement

A subject and its verb should agree in number. Singular subjects generally require singular verbs, while plural subjects require plural verbs.

For example:

Incorrect: The list of requirements are included below.
Correct: The list of requirements is included below.

Words between the subject and verb can make agreement mistakes easier to miss.

Pay particular attention to sentences with long phrases between the subject and its verb.

Its vs. It’s

These two words are commonly confused in professional writing.

Its indicates possession.
It’s is a contraction of “it is” or “it has.”

For example:

Incorrect: The organization updated it’s policy.
Correct: The organization updated its policy.

Because both words are correctly spelled, spellcheck may not catch the mistake.

Your vs. You’re

Another common error involves confusing your and you’re.

Your indicates possession.
You’re means “you are.”

For example:

Incorrect: Please review you’re report.
Correct: Please review your report.

These words are easy to confuse because they sound alike in everyday speech.

Their, There, and They’re

These three words have different meanings and should not be used interchangeably.

Their indicates possession.
There refers to a place or introduces a statement.
They’re means “they are.”

For example:

Their report was submitted yesterday.
The files are over there.
They’re responsible for reviewing the documents.

Spellcheck may not catch an error when the incorrect word is spelled correctly.

Affect vs. Effect

Affect and effect are frequently confused because their meanings and grammatical uses can be similar in some contexts.

In general:

Affect is usually a verb meaning to influence.
Effect is usually a noun meaning a result.

For example:

The policy may affect employee retention.

The policy had a significant effect on employee retention.

These words require attention to both meaning and context.

Fewer vs. Less

Use fewer with things that can be counted individually and less with things considered as a quantity or amount.

For example:

Fewer employees attended the meeting.
The project required less time than expected.

This distinction is particularly useful when writing reports and other documents that include quantitative information.

Who vs. Whom

Who is generally used as a subject, while whom is used as an object.

For example:

Who submitted the report?
To whom should the report be sent?

Although “whom” is less common in everyday conversation, it may still appear in formal professional writing.

Pronoun Agreement

Pronouns should agree with the nouns they refer to in number and, when applicable, person.

For example:

Incorrect: Each employee should submit their form by Friday.
Correct: Employees should submit their forms by Friday.

Singular they is also widely accepted in many modern style guides and can be useful when a person’s gender is unknown or irrelevant.

Follow the organization’s preferred style guide when making these decisions.

Misplaced Modifiers

A modifier should be placed close enough to the word or phrase it modifies that the meaning is clear.

For example:

Unclear: After reviewing the report, several errors were identified.
Clearer: After reviewing the report, the editor identified several errors.

The first sentence suggests that the errors reviewed the report.

Careful sentence construction prevents this type of confusion.

Parallel Structure

Items in a series should follow the same grammatical structure.

For example:

Inconsistent: The position requires writing reports, reviewing documents, and communication with clients.
Parallel: The position requires writing reports, reviewing documents, and communicating with clients.

Parallel structure makes lists and comparisons easier to read.

Comma Splices

A comma splice occurs when two independent clauses are joined with only a comma.

For example:

Incorrect: The report is complete, it needs to be proofread.
Correct: The report is complete, but it needs to be proofread.

Other options include separating the clauses with a period or using a semicolon when appropriate.

Sentence Fragments

A sentence fragment is an incomplete sentence that’s presented as though it were a complete thought.

For example:

Fragment: Because the report was incomplete.
Complete: The report was delayed because it was incomplete.

Fragments can sometimes be intentional in headings or other contexts, but they should be corrected when they interfere with professional writing.

Run-On Sentences

A run-on sentence occurs when multiple independent clauses are improperly joined.

For example:

Incorrect: The report is complete we can send it to the board.
Correct: The report is complete, so we can send it to the board.

Breaking overly long sentences into shorter, focused sentences can also improve readability.

Apostrophe Errors

Apostrophes are often misused in possessives and contractions.

For example:

Its policy, not it’s policy (when referring to a certain company or organization’s policy, i.e., The company cannot change its policy).
Employees’ responsibilities when referring to multiple employees
Employee’s responsibility when referring to one employee

Plural nouns don’t automatically require an apostrophe.

Capitalization Errors

Professional documents often contain organization-specific terms, titles, departments, programs, and initiatives that require consistent capitalization.

Review capitalization for:

Job titles
Department names
Program names
Organization names
Headings
Defined terms
Government or institutional titles

A style guide can help determine when capitalization is appropriate.

Inconsistent Verb Tense

Verb tense should remain consistent unless there’s a clear reason to shift between past, present, and future.

For example:

Inconsistent: The organization launched the program in 2024 and continues to expand it in 2025.

This sentence may be correct because it describes two different time periods. However, unnecessary shifts in tense can make writing confusing. Review tense changes carefully to make sure each one serves a purpose.

Confusing Word Pairs

Some commonly confused words are spelled correctly but have different meanings.

Examples include:

Principal / principle
Compliment / complement
Stationary / stationery
Accept / except
Then / than
Lead / led
Ensure / insure
Advice / advise

Because both words in each pair are legitimate words, automated spellcheck may not identify an incorrect usage.

Overly Complicated Sentences

Not every grammatical sentence is an effective sentence.

Professional writing can become difficult to follow when sentences contain too many clauses, unnecessary qualifiers, or excessive detail.

Consider breaking long sentences into shorter ones when:

The main point is difficult to identify
Several ideas are being communicated at once
Multiple clauses make the sentence difficult to follow
Readers may need to reread the sentence
Important information is buried in the middle

Clear writing doesn’t require complicated sentences.

Inconsistent Punctuation

Punctuation should be consistent throughout a document.

This is especially important for lists, headings, quotations, abbreviations, and numbers.

Review the document for consistency in:

Commas
Semicolons
Colons
Apostrophes
Quotation marks
Hyphens
Parentheses
Periods in bulleted lists

The appropriate treatment may depend on the organization’s style guide.

Give Professional Writing a Careful Review

Grammar mistakes can be small, but they can affect the clarity and professionalism of an important document. A careful review can catch errors that spellcheck may overlook and help ensure that the writing is consistent from beginning to end.

At SP Editing, we provide professional copy editing and proofreading services for reports, policies, manuals, strategic plans, and other organizational documents. We help nonprofits, government agencies, educational institutions, healthcare organizations, and businesses improve grammar, clarity, consistency, and overall readability while preserving the intended meaning of their content.

Before an important document reaches its audience, let SP Editing give it the careful editorial review it deserves.

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