10 Grammar Mistakes CELPIP Candidates Make (And How to Fix Them)

Why Grammar Errors Cost More Than You Think

In CELPIP, the Grammar Accuracy criterion is scored separately from Vocabulary, Task Achievement, and Coherence. But grammar errors do more than just lower your Grammar score — they can reduce your Coherence score by making sentences harder to follow, and they can lower your Task Achievement score if they obscure your intended meaning.

The 10 mistakes below come up repeatedly in writing and speaking responses at the CLB 5–8 range. Each one is fixable with a clear rule to remember.

Mistake 1: Subject-Verb Agreement with Group Nouns

Before: "My team are ready to present." After: "My team is ready to present."

In Canadian English, collective nouns — team, staff, committee, family, government — take singular verbs. This differs from British English, where both forms are accepted. CELPIP uses Canadian English conventions.

The rule: If the noun refers to a group acting as a unit, use a singular verb. "The committee has voted." "The staff is available." "Our family is coming."

Mistake 2: Tense Inconsistency Within a Response

Before: "I went to the meeting and then I tell my manager about the issue." After: "I went to the meeting and then I told my manager about the issue."

Shifting tense mid-paragraph without reason confuses the reader and signals poor grammatical control. Choose a tense at the start of each section and stay in it.

The rule: For past events, use simple past throughout. For recommendations or general truths, use simple present. Only shift tenses when the timeframe genuinely changes.

Mistake 3: Missing Articles (a, an, the)

Before: "I need information about parking situation near office." After: "I need information about the parking situation near the office."

Missing articles are one of the clearest indicators of non-native English in writing. They affect both grammar accuracy and the reader's experience.

The rule: Use the when both speaker and listener know which specific thing you mean. Use a/an when introducing something for the first time or when one of a category. Use nothing when referring to things in general ("I like coffee," "information is useful").

Mistake 4: Confusing 'which' and 'that' in Relative Clauses

Before: "The report which I submitted last week is missing." After: "The report that I submitted last week is missing."

In Canadian written English, that is used for restrictive relative clauses (those that narrow down which specific thing you mean). Which introduces non-restrictive clauses, which are set off by commas and add extra information about something already specific.

The rule: No comma → use that. Comma + extra info → use which.

• "The form that I filled out was incorrect." (restrictive — which specific form)
• "The form, which I filled out yesterday, was incorrect." (non-restrictive — the form is already identified)

Mistake 5: Incorrect Prepositions After Common Verbs

Before: "I am interested on your proposal." After: "I am interested in your proposal."

Preposition errors are extremely common because preposition use is largely fixed in English — there is no rule to derive them, only patterns to learn.

High-frequency correct prepositional phrases:

• interested in, not interested on
• agree with (a person), agree to (a proposal)
• apologise for, not apologise about
• responsible for, not responsible of
• apply for, not apply to (for a position)
• depend on, not depend of

Mistake 6: Overusing Continuous Tense

Before: "I am thinking that the schedule is needing to be adjusted." After: "I think the schedule needs to be adjusted."

Present continuous (am/is/are + -ing) describes actions happening right now in real time. Certain verbs — called stative verbs — describe states rather than actions and are almost never used in continuous form.

Common stative verbs that do not take -ing: think, know, understand, believe, want, need, have (possession), see, hear, prefer, remember

The rule: If the verb describes a mental state, emotion, or possession, use simple present. "I understand the situation." "She wants a refund." "He knows the answer."

Mistake 7: Run-On Sentences Joined Only With 'and'

Before: "I work as a nurse and I have been doing this for five years and I am now looking for new opportunities and I want to apply for a management position." After: "I have worked as a nurse for five years. I am now looking for new opportunities and hope to apply for a management role."

Chaining multiple independent clauses with "and" is grammatically tolerable but reads as low-complexity writing. Each "and" is a missed opportunity to use a subordinating conjunction, a semicolon, or a sentence break.

The rule: Limit compound sentences to two clauses joined by a conjunction. Start a new sentence for the third idea.

Mistake 8: Wrong Form After Modal Verbs

Before: "You should to submit the form by Friday." After: "You should submit the form by Friday."

Modal verbs (can, could, should, would, must, may, might, will) are always followed by the base form of the verb — the infinitive without "to."

The rule: Modal + base verb (never modal + to + verb).

• "You should go." NOT "You should to go."
• "She can help." NOT "She can to help."
• "They must confirm." NOT "They must to confirm."

Mistake 9: Apostrophe Errors with Possession and Contractions

Before: "The managers decision affected everyones schedule." After: "The manager**'s** decision affected everyone's schedule."

Also common: confusing it's (it is) with its (possessive).

Before: "The company changed it's policy last month." After: "The company changed its policy last month."

The rule:

• Possession: noun + 's → "the manager's decision," "everyone's schedule"
• "It's" = "it is" (contraction). "Its" = belonging to it (no apostrophe).
• Contractions like "it's" are slightly informal. In formal emails or essays, prefer "it is" to avoid confusion.

Mistake 10: Unclear Pronoun Reference

Before: "When the manager met with the client, he was very difficult." After: "When the manager met with the client, the client was very difficult."

Pronoun reference errors occur when "he," "she," "they," or "it" could logically refer to more than one noun. The reader cannot tell who "he" is — the manager or the client.

The rule: If repeating the noun feels awkward but the pronoun is unclear, use the noun anyway. Clarity is more important than elegance. Alternatively, restructure the sentence so the pronoun follows its referent closely: "The client was very difficult during his meeting with the manager."

How to Use This List in Your Practice

Do not try to memorise all 10 at once. Instead:

1. Take a practice writing session and identify which mistakes appear in your response.
2. Focus on the 2–3 patterns that come up most frequently in your writing.
3. After your next session, check specifically for those patterns before submitting.

Grammar improvement is cumulative. Eliminating one consistent error per week over 10 weeks creates a meaningfully cleaner response by exam day.