Substitution with Do So, So and Not (C1)

Substitution avoids repetition while keeping a clear link to earlier information. Do so replaces a verb phrase; so and not can stand for a whole clause. Choosing between them depends on meaning, the surrounding verb and register.

What is being replaced?

A substitute must have a clear antecedent: the earlier expression that supplies its meaning. Identify whether you are referring back to an action or to a proposition—something presented as true, possible or expected.

Substitute	What it replaces	Example
do so	A verb phrase describing an action or event	Maya checked the figures, and Leo did so too.
so	A clause expressing a proposition	“Are the figures accurate?” “I believe so.”
not	The negative version of a proposition	“Will we need another audit?” “I hope not.”

In the first example, did so means checked the figures. In the second, so means that the figures are accurate. In the third, not means that we will not need another audit.

Using do so

Use do so to refer back to an action or event without repeating its verb phrase. The form of do changes to fit the tense and grammatical structure; so stays unchanged.

The editor promised to check the references and did so immediately.
Anyone wishing to withdraw their application must do so by Friday.
She apologised publicly. By doing so, she helped restore trust.
They were asked to destroy the records, but they may already have done so.

The subject does not have to remain the same. You can also add a contrasting time, manner or other circumstance:

Nina submitted her report on Monday; Omar did so on Tuesday.
The first team checked the equipment manually; the second did so automatically.

Here, do so replaces the shared action, while the new expression supplies a different circumstance.

Actions, events and states

Do so works most naturally with dynamic situations—actions or events—rather than states such as possession, knowledge or resemblance. The subject need not be human: The first engine failed at noon; the second did so an hour later.

Do not use do so as a general replacement for any verb.

Unnatural for the intended meaning: Eva knows the answer, and Max does so too.

Natural: Eva knows the answer, and Max does too.

The second sentence uses auxiliary ellipsis, not do so substitution.

Register and clear reference

Do so is particularly useful in formal instructions, reports and carefully structured writing. It also occurs in speech, but do it, do that, or a shorter auxiliary construction may sound more conversational.

Compare:

Formal instruction: If you wish to appeal, please do so within fourteen days.
Conversation: “Have you sent the email?” “Yes, I have.”
Reaction to an action: “I'm going to delete the backup.” “Don't do that!”

These expressions are not always interchangeable. Do so normally depends on an action or event already expressed in words. Do it and do that can also refer to an action evident from the situation.

Before using do so, expand it mentally. If the reader could recover two different actions, repeat the intended verb phrase instead.

Unclear: The assistant promised to contact the client and revise the invoice. She did so that afternoon.

Clearer if only one action is intended: She revised the invoice that afternoon.

Quick check

Try one question now.

The north lift stopped unexpectedly at nine; the south lift twenty minutes later.

Check your answer when you are ready. No sign-in needed.

So as a clause substitute

After certain verbs, so replaces a clause rather than an action. Common patterns include think so, believe so, suppose so, expect so, hope so and say so.

“Has the deadline changed?”

“I think so.” — That is my opinion, but I am not certain.
“I hope so.” — I want the deadline to have changed.
“The coordinator said so.” — The coordinator stated that it had changed.

The verb still contributes its own meaning: belief, expectation, hope or a report. So does not make these responses equivalent.

This pattern is restricted to particular verbs. Do not assume that every verb followed by a that-clause can take so.

Natural: “Is she available?” “I know she is.”
Not standard for this meaning: “I know so.”

A related reporting pattern places so first: The road is closed, or so I hear. This attributes the information to a report rather than presenting it as direct knowledge.

Distinguish substitution from agreement and confirmation:

“I think so.” — So replaces a proposition.
“So do I.” — The speaker shares someone else's view or experience.
“So it is!” — The speaker recognises or confirms something.

The word order reflects different constructions, not freely interchangeable versions of one pattern.

Choosing a negative response

To reject the proposition, English uses either not as the substitute or a negative verb followed by so. The preferred pattern depends on the verb.

Pattern	Natural negative response	Register or preference
hope so	I hope not.	Normal pattern; avoid I don't hope so for this meaning.
think so	I don't think so. / I think not.	The first is usual; the second sounds formal or emphatic.
believe so	I don't believe so. / I believe not.	The second is more formal.
expect so	I don't expect so. / I expect not.	Both are possible.
suppose so	I suppose not. / I don't suppose so.	Both are possible.
be afraid so	I'm afraid not.	Often introduces an unwelcome answer politely.

“Will the repairs take another week?”

“I hope not.” — I want them not to take another week.
“I don't think so.” — My judgement is that they probably will not.
“I'm afraid so.” — Unfortunately, I believe they will.

With reporting verbs, negative placement can change the message. She didn't say so means that she did not state the proposition; it does not mean that she stated its opposite.

Similarly, I don't think so normally communicates a negative opinion, but it need not express absolute certainty.

A practical checklist

Identify the reference: an action or event suggests do so; a proposition may allow so or not.
Check the construction: use do so with suitable dynamic meanings and clause-substitute so only with verbs that allow it.
Choose the negative pattern: prefer hope not, don't think so and I'm afraid not in their usual contexts.
Check the meaning: not reporting something is different from reporting that it is false.
Check clarity and register: use substitution to reduce repetition, but repeat the wording when the reference would otherwise be unclear.

1.What is being replaced?

2.Using do so

2.1Actions, events and states

3.Register and clear reference

Try one question now.

4.So as a clause substitute

5.Choosing a negative response

6.A practical checklist

Now make it stick.