Page 181 - Practical English Usage 3ed - Michael Swan, Oxford

Progressive forms are possible, but not very common. You should be getting dressed. - I am (doing).
Note that the auxiliary verb is stressed in this structure. Close the door. - I HAVE done. (NOT •••: have DONE.)
For auxiliary verbs used instead of complete verb phrases, see 181.
162 do so/it/that
1 doso
The expression do so can be used to avoid repeating a verb and its object or complement. It is usually rather formal.
Put the car away, please. - I've already done so.
Eventually she divorced Stephen. It was a pity she had not done so earlier. He told me to get out, and I did so as quietly as possible.
2 do so and do itlthat
Do it and do that can be used instead of do so.
I promised to get the tickets, and I will do so/it as soon as possible. She rode a camel: she had never done so/that before.
We use do so mainly to refer to the same action, with the same subject, that was mentioned before. In other cases we prefer do it/that or do alone.
I haven't got time to get the tickets. Who's going to do it? (NOT • • . Yllw's gtJi1lK t6 d6 S6?)
I rode a camel in Morocco. - I'd love to do that. (NOT ••• t6 d6 S6.)
I always eat peas with honey, My wife never does. (N OT • • • lAy wife ncver tl6es
S6;)
3 do sO/itlthat deliberate actions
Do so/it/that are mainly used to refer to deliberate dynamic actions. We do not usually use these expressions to replace verbs like fall, lose, like, remember, think, own, which refer to involuntary actions or states.
I like the saxophone, and I always have (done). (NOT ••• and I have always dane selithhat.)
She lost her money. I wasn't surprised that she did.
r.._ , ..1:..1 ,., r.. ) (NOT .. .... tnat Si1e Uta 36Jltrfrltl;t.
I think Jake's wrong. I did when he first spoke to me.
r ..1:..1 ,., I ,
(NOT • • • • uta StJittttttat tth1el'l •••
4 other verbs
)
Note that so, it and that are not normally used in this way after auxiliary verbs. It is not possible in standard English to say [ can so, She was it or [ have that.
For so 1am. so it is etc, see 541.2.
For so do I, so am 1etc, see 541.1.
For so with say and tell, see 540.
For so with thillk, believe, hope and similar verbs, see 539.
For auxiliary do as substitute for a whole verb phrase, see 181. For differences between it and that, see 590.
do so/it/that 162
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