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TOEIC Link Part 5 — Not Only But Also: When It Inverts, and What Must Stay Parallel

Not only ... but also is a correlative pair that fails Part 5 takers two ways: they forget that fronting Not only inverts the verb, and they break the parallelism the pair demands on both sides. This guide separates the mid-sentence form that stays normal from the sentence-initial form that inverts, gives you the parallelism test that catches mismatched word classes, and works the distractor logic on workplace items.

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Not only ____ the new plant reduce costs, but it also shortened delivery times. The options offer did, had, does, and it. Learners who read this as an ordinary sentence pick it to keep subject-first order and lose the mark. The answer is did, and reaching it means recognizing that not only, when it opens the clause, forces the same inversion as any fronted negative adverbial. This guide sorts out when not only ... but also inverts and when it does not, and the parallelism it always demands.

Two positions, two behaviors

Not only ... but also behaves in two completely different ways depending on where not only sits, and TOEIC tests both:

  • Mid-sentence (after the subject and verb): no inversion. The plant not only **reduced** costs but also **shortened** delivery times. Normal order — not only just introduces the first of two things the plant did.
  • Sentence-initial (fronted for emphasis): inversion. **Not only did** the plant reduce costs, but it also shortened delivery times. Fronting the negative not only flips subject and auxiliary into question-like order — exactly the mechanism behind no sooner ... than and hardly ... when inversion.

The opening item fronts Not only, so it must invert: Not only **did** the new plant reduce.... it keeps subject-first order and is the trap; did supplies the inverted auxiliary. When you see Not only as the first word of the sentence, expect an auxiliary right after it.

Which auxiliary to insert

When the fronted form needs a supporting auxiliary, match it to the tense and person of the underlying verb:

  • Past simple → did: Not only **did** she lead the project...
  • Present simple → does/do: Not only **does** the tool track hours...
  • Perfect or modal → the existing auxiliary fronts directly: Not only **has** the team shipped..., Not only **can** the system scale...

In the opening item, the second clause shortened fixes the timeframe as past, so the fronted auxiliary is did, not does. Read the other clause to pin the tense when the blank hides it.

The parallelism the pair always demands

Whether or not it inverts, not only ... but also is a correlative pair, and correlatives require the element after each half to be the same word class or structure. Break that symmetry and the sentence is wrong even when the meaning is clear:

  • ✗ The role requires not only **technical skill** but also **to communicate well**. (noun vs. infinitive)
  • ✓ The role requires not only **technical skill** but also **strong communication**. (noun vs. noun)
  • ✓ The role requires the candidate not only **to code** but also **to communicate**. (infinitive vs. infinitive)

The test is mechanical: cover everything between not only and but also, read what follows each, and confirm they are the same grammatical shape — both nouns, both verbs, both prepositional phrases, both clauses. This is the identical discipline you apply across the whole correlative family; drill it with correlative conjunctions like either/or and neither/nor, where the same parallelism trap appears with different partner words.

Distractor logic on the page

Part 5 builds distractors for this construction three ways:

  1. The no-inversion trap in a fronted sentence. The option keeps subject-first order after an initial Not only. Eliminate it — fronting forces inversion.
  2. The wrong auxiliary. does where the sister clause is past, or did where it is present. Check the other clause's tense.
  3. The broken-parallel option. The blank sits after but also and offers a word class that does not match what followed not only. Run the cover-and-compare test.

Worked examples

  • Not only ____ the vendor miss the deadline, but it also raised its rates. → did (fronted inversion; past, fixed by raised).
  • The upgrade improved not only **speed** but also ____. → choose the noun (e.g. reliability), not a verb phrase — parallelism after not only speed.
  • Not only ____ the report been reviewed, but it has also been approved. → has (perfect auxiliary fronts directly).
  • She not only **manages** the budget but also ____ the vendors. → a present-tense verb (negotiates), parallel to manages; no inversion here because not only is mid-sentence.

The one habit that makes this automatic

Before you answer any not only ... but also item, ask one question first: is not only the opening word, or is it tucked after the subject? That single check decides whether you are hunting for an inverted auxiliary or an ordinary parallel element. Front position → invert and supply an auxiliary; mid position → keep normal order and match the verb. Then run the cover-and-compare parallelism test on both halves. Two checks, and this high-frequency construction stops being a guess.