TOEIC Link Writing — Restrictive and Non-Restrictive Relative Clause Punctuation

On the TOEIC Link Writing module, a single comma before a relative clause can change what a sentence claims. The employees who completed the training received a bonus says that only the trained employees got the bonus; the employees, who completed the training, received a bonus says that all the employees got it and, incidentally, all of them had completed the training. The words are identical; the commas carry the meaning. Raters read this distinction as a direct test of whether a writer controls the relationship between a noun and the clause that modifies it, and getting it wrong does not merely look untidy — it states something the writer did not intend.

This article covers the meaning difference between restrictive and non-restrictive clauses, the three punctuation errors that most often cost band points, when that and which are and are not interchangeable, and a four-week sequence that installs the distinction as a drafting reflex rather than a proofreading repair.

What the two clause types actually do

A restrictive relative clause identifies which noun the writer means. It narrows the reference from a larger set to a specific member, and because it is essential to the identification it takes no commas. The report that the auditor flagged needs revision tells the reader which of several reports needs revision — the one the auditor flagged — and removing the clause would leave the sentence unable to point at anything. The clause is load-bearing, so no comma separates it from the noun.

A non-restrictive relative clause adds information about a noun whose identity is already settled. It does not narrow the reference; it comments on an item the reader can already locate, and because the information is supplementary it is fenced off with commas. The Q3 report, which the auditor flagged, needs revision names a specific report — there is only one Q3 report — and then adds that the auditor flagged it. Remove the clause and the sentence still points at the same report. The commas signal that what sits between them could be lifted out without changing which noun is meant.

The test is mechanical: if removing the clause would leave the reader unable to tell which noun is meant, the clause is restrictive and takes no commas; if removing it leaves the reference intact, the clause is non-restrictive and takes commas. This is the same essential-versus-supplementary judgment that governs the boundary punctuation covered in semicolon, colon, and dash deployment for clause-boundary control, applied here to the narrower case of the relative clause.

The three punctuation errors that cost band points

The first error is the comma-splice restrictive clause — inserting a comma before a clause that is doing identifying work. The candidates, who submitted late, were disqualified tells the reader that all candidates were disqualified and all of them submitted late, when the writer meant that only the late submitters were disqualified. The comma has quietly universalized a claim the writer intended to restrict. Because both readings are grammatical, the rater cannot rescue the intended meaning; the sentence says what its punctuation says.

The second error is the missing comma on a non-restrictive clause, the mirror fault. The CEO who founded the company in 1990 will retire implies there is more than one CEO and specifies which — the founding one — when a company has a single current CEO and the founding fact is merely supplementary. The absent commas turn an aside into an identifier and imply a set of CEOs that does not exist. With a proper noun or any inherently unique referent, a following relative clause is almost always non-restrictive and needs its commas.

The third error is the half-fenced non-restrictive clause — opening the aside with a comma but forgetting to close it, or closing without opening. The proposal, which the board approved will proceed opens the fence and never closes it, so the reader loses track of where the aside ends and the main clause resumes. A non-restrictive clause embedded mid-sentence needs commas on both sides; the pair works together, and dropping either one breaks the signal.

When that and which are interchangeable

That can only introduce a restrictive clause. Which can introduce either, but the higher bands, and most style guidance the raters are calibrated to, reserve which for non-restrictive clauses and use that for restrictive ones. So the invoice that arrived today (restrictive, no comma, that) and the March invoice, which arrived today (non-restrictive, commas, which) form the clean pattern. Writing the invoice which arrived today without commas is not wrong in every register, but it blurs the restrictive-versus-non-restrictive signal precisely where the module rewards clarity. The reliable rule for the exam: restrictive takes that and no commas; non-restrictive takes which and commas. Note also that who and whom follow the same comma logic for people — the presence or absence of commas, not the choice of relative pronoun, is what encodes restriction. Controlling this distinction is part of the same clause-management competence developed in clausal subordination and syntactic complexity calibration.

The four-week training sequence

Week one is recognition. Take model paragraphs at the target register, mark every relative clause, and for each one decide whether removing it would leave the reader unable to identify the noun. Then check whether the punctuation matches your judgment. The goal is to see each relative clause as a fork where an essential-versus-supplementary decision has already been made and encoded in commas.

Week two is directed correction. Take sentences where the comma choice contradicts the intended meaning — a comma-spliced restrictive clause, a comma-less non-restrictive one, a half-fenced aside — and repair each, stating the meaning the corrected punctuation now carries. This trains the eye to read commas as claims rather than as decoration.

Week three is pronoun drilling. Write paired sentences for the same noun — one restrictive with that and no commas, one non-restrictive with which and commas — and confirm that each pair encodes two genuinely different claims. Building both members of the pair fixes the mapping between pronoun, punctuation, and meaning.

Week four is integration. Draft full responses under exam timing with no separate punctuation pass, then reread checking that every relative clause carries the commas its meaning requires. When restrictive clauses come out comma-free and non-restrictive ones come out fully fenced in the first draft, the control has moved from proofreading into drafting, which is the state the higher bands reward.

The takeaway

On TOEIC Link Writing, the comma before a relative clause is not cosmetic — it decides whether the clause identifies the noun or merely comments on it. Use no commas when the clause is essential to knowing which noun is meant, and a matched pair of commas when it is supplementary. Reserve that for restrictive clauses and which for non-restrictive ones, and never leave a non-restrictive aside half-fenced. Train recognition first, then correction of the three errors, then paired-pronoun drilling under time, until the punctuation states exactly the claim you intend on the first pass.