The 10 Most Common Grammar Mistakes on the TOEIC (and How to Avoid Them)

The grammar section of the TOEIC (Part 5 and Part 6) is a goldmine of easy points — to gain or to lose. The same traps come up test after test, and the good news is that once you know them, you won't fall for them again.

Here are the 10 most common mistakes candidates make, with concrete examples and the rule to remember for each one.

1. Confusing the Present Perfect and the Past Simple

This is the number one mistake on the TOEIC. Both tenses talk about the past, but not in the same way.

Trick question:

❌ The company has launched a new product last year.
✅ The company launched a new product last year.

The rule: if the sentence contains a specific time marker (last year, in 2024, yesterday), use the past simple. The present perfect is used when the time is not specified or when the action is connected to the present.

✅ The company has launched three products this year. (unfinished time period)

2. Choosing the Wrong Word Form

The TOEIC loves testing whether you can distinguish a noun, an adjective, an adverb, and a verb.

Trick question:

❌ The manager made a decide quickly.
✅ The manager made a decision quickly.

The rule: look at the word's position in the sentence.

After an article (a, the) or an adjective → noun (decision, improvement)
Before a noun → adjective (significant, annual)
After a verb → adverb (quickly, efficiently)

3. Confusing Despite, Although, and However

These three words express opposition, but they are used differently.

Trick question:

❌ Despite the weather was bad, we continued.
✅ Although the weather was bad, we continued.
✅ Despite the bad weather, we continued.

The rule:

Despite / In spite of + noun or gerund (despite the rain, despite being late)
Although / Even though + subject + verb (although it rained)
However = beginning of a new sentence (However, we continued.)

4. Mixing Up Infinitive and Gerund

Some verbs are followed by the infinitive, others by the gerund. The TOEIC tests this systematically.

Trick question:

❌ The team enjoys to work on new projects.
✅ The team enjoys working on new projects.

Common TOEIC verbs:

+ gerund (-ing): enjoy, consider, avoid, suggest, recommend, postpone
+ infinitive (to): decide, agree, plan, expect, offer, refuse

5. Subject-Verb Agreement Errors

When the subject and verb are separated by a long phrase, many candidates lose track.

Trick question:

❌ The list of required documents are available online.
✅ The list of required documents is available online.

The rule: the verb agrees with the main subject, not the nearest word. Here, the subject is the list (singular), not documents.

Also watch out for:

Each / Every + singular verb (Each employee is responsible...)
The number of + singular verb (The number of applicants has increased.)
A number of + plural verb (A number of applicants have applied.)

6. Wrong Prepositions

Prepositions in English don't translate directly from other languages. You need to learn them by heart.

Classic TOEIC traps:

❌ responsible of → ✅ responsible for
❌ comply to → ✅ comply with
❌ interested for → ✅ interested in
❌ depend of → ✅ depend on
❌ result of a change → ✅ result in a change

The rule: there really isn't one. Learn verb + preposition combinations as fixed blocks. It's vocabulary, not grammar.

7. Confusing Relative Pronouns (Who, Which, That)

Trick question:

❌ The report who was submitted yesterday...
✅ The report that / which was submitted yesterday...

The rule:

Who → people (The employee who applied...)
Which → things (The report which was sent...)
That → people and things (common usage)
Whose → possession (The client whose order was delayed...)

8. Forgetting the Passive Voice When Needed

The TOEIC uses the passive voice extensively, especially in professional contexts.

Trick question:

❌ The meeting postponed to next week.
✅ The meeting was postponed to next week.

The rule: if the subject receives the action (it doesn't perform it), use the passive: be + past participle.

Common TOEIC forms:

is expected to...
was approved by...
has been scheduled for...
will be reviewed by...

9. Confusing Much, Many, Few, and Little

Trick question:

❌ There are much employees in the office.
✅ There are many employees in the office.

The rule:

Many / Few → countable nouns (many reports, few candidates)
Much / Little → uncountable nouns (much information, little time)

TOEIC tip: if the noun is plural, it's always many or few.

10. Wrong Conditional Form

The TOEIC tests all three types of conditionals.

Trick question:

❌ If the budget will increase, we can hire more staff.
✅ If the budget increases, we can hire more staff.

The rule:

If + present → future result (If it rains, we will cancel.)
If + past simple → hypothetical situation (If we had more time, we would improve it.)
If + past perfect → regret about the past (If we had known, we would have acted differently.)

Classic trap: never put will in the if clause (except in very rare cases).

How to Stop Making These Mistakes

Learn the rules one by one: don't try to master everything in a week. Focus on one mistake per day.
Do targeted exercises: practice each grammar point with TOEIC-format questions.
Analyze your mistakes: every time you get something wrong, identify which rule you forgot.
Train in real conditions: Part 5 requires speed. Aim for 30 seconds per question maximum.

On FluencyGo, you can practice with exercises sorted by grammar skill and review only the questions you got wrong, so you can improve more efficiently.

Key Takeaways

These 10 mistakes account for the majority of grammar points lost on the TOEIC. The good news is that the same traps come up every time. By mastering them, you can easily gain 50 to 100 points on your total score.

Start by identifying which of these mistakes you make most often, and work on those first.