So Do I / Neither Do I

"So do I" and "Neither do I" are short agreement responses used when you share the same experience, opinion, or situation as another person. They are the English equivalent of "me too" and "me neither" — but with a specific grammatical structure that trips up learners at every level.

The good news: there are only 2 patterns and 1 rule.

The 1 Rule: Match the auxiliary.

The auxiliary verb in your response must match the auxiliary (or "be" / modal) in the original statement. This is where the real challenge lies — and the focus of this entire lesson.

Word order is inverted: It's So do I, not So I do. The auxiliary comes before the subject — the same inversion used in questions. (We'll cover the special meaning of "So I do" later.)

Present Tenses: Do/Does & Am/Is/Are

At A2 level, you need to handle two types of auxiliaries in the present tense: do/does (for action verbs) and am/is/are (for "be").

Action Verbs → Do / Does

When the original statement uses a main verb (not "be"), use do or does in your response.

"Be" → Am / Is / Are

When the original statement uses "be" (am/is/are), match the form of "be" — not "do".

The #1 Trap: Do vs Am/Is/Are

⚠️ Error Zone — This is the most common mistake at every level.

Students often use "do" when they should use "am/is/are" (or vice versa). The rule is simple:

Original verb	Use	Example
Action verb (like, speak, work...)	do / does	"I like tea." → "So do I."
"Be" (am, is, are)	am / is / are	"I'm tired." → "So am I."

• ❌ "I'm hungry." → "So do I." (wrong — "am" not "do")
• ❌ "I enjoy reading." → "So am I." (wrong — "do" not "am")

Quick test: Is there an action verb? → do/does. Is it a form of "be"? → use that form of "be".

Subject Agreement

The auxiliary must also agree with the new subject (not the original one):

👉 Practice So & Neither — Present Tenses →

Past, Perfect & Modals

At B1 level, you need to extend the same pattern to past simple, past continuous, present perfect, past perfect, and modal verbs.

Past Simple → Did

For past simple action verbs, the auxiliary is always did — regardless of the subject.

Watch out: "Was/were" is NOT the auxiliary for past action verbs. "I went" → "So did I" (not So was I). Only use "was/were" when the original uses "be" in the past.

Past "Be" → Was / Were

Present Perfect → Have / Has

Past Perfect → Had

Modal Verbs → Keep the Same Modal

With modals, simply repeat the same modal verb — don't change it.

Never change the modal. If the original uses "can", don't switch to "could" or "do". If it uses "would", don't switch to "will". Match it exactly.

👉 Practice So & Neither — Past, Perfect & Modals →

Too, Either & "So I Do"

Informal Alternatives: Too & Either

In casual conversation, many speakers prefer simpler structures with too (affirmative) and either (negative):

Rules:

• Too goes at the end of an affirmative response: I do too.
• Either goes at the end of a negative response: I don't either.
• Me too / Me neither are the most casual — perfectly natural in speech but avoid in formal writing.

"So Do I" vs "So I Do" — Agreement vs Emphasis

These look nearly identical but have completely different meanings:

• "I enjoy cooking." → "So do I." (= me too — I also enjoy cooking)
• "You always take the bus, don't you?" → "So I do — but today I'm driving." (= yes, that's right, I do)

"So I do" confirms something someone said about you. "So do I" says you share the same experience. Mixing these up changes the meaning completely.

"Have" as Main Verb vs Auxiliary

Be careful with "have" — it can be a main verb (possession) or an auxiliary (present perfect):

When "have" means "possess" in present simple, treat it like any other main verb and use do/does.

For more on how auxiliary verbs work across all tenses, see Auxiliary Verbs. The skill of matching auxiliaries is also essential for Tag Questions.

👉 Practice Mixed So, Neither, Too & Either →

Common Mistakes to Avoid

Quick Summary

Step-by-Step Guide

Step 1 — Is the original statement affirmative or negative?

Step 2 — Identify the auxiliary verb in the original:

Step 3 — Make sure the auxiliary agrees with the NEW subject:

Step 4 — Assemble: So/Neither + auxiliary + subject

Informal Alternatives

Practice Tips

1. Drill the auxiliary identification: The entire skill depends on spotting the right auxiliary. Take any sentence and ask: "What's the auxiliary?" Present simple → do/does. Present perfect → have/has. Modal → the modal itself. Speed up this recognition and the responses become automatic.

2. Practise with real conversations: When someone tells you something, mentally form the "So do I" / "Neither do I" response — even if you don't say it aloud. This builds the habit of matching auxiliaries in real time.

3. Watch out for "be" vs action verbs: Every time you want to respond, pause and ask: "Is the original using 'be' or an action verb?" This single check prevents the #1 error.

4. Learn the "too/either" alternatives as a pair: Always learn them together — too for affirmative, either for negative. If you remember the pair, you'll never mix them up.

5. Test yourself across all tenses: Write one statement in each tense (present simple, past simple, present perfect, future, modal) and create both a "So..." and "Neither..." response for each. This systematic practice covers all the auxiliary patterns.

Practice All Exercises

Practise so do I and neither do I agreement responses with multiple choice exercises online — every question comes with answers and explanations. These so and neither exercises cover auxiliary verb matching across all tenses and modals from A2 to B1:

Now try the exercises to practice what you've learned!