Verbs with other meaningsThere is one verb, do, which does not fit into the above meaning group. This has the affirmative do so only - the negative is formed with an auxiliary or modal.
Do so can be used to stand for any verbal group. It usually refers back to another verbal group, which may be one in a previous sentence. Do so has an important function in repeating given information while introducing something new. In the first example below, was doing so repeats the information had telephoned the police while the new information in the clause is Mr X had come to stand directly in front of him...
Bailiff B had telephoned the police. While he was doing so, Mr X had come to stand directly in front of him, shouting at him to get out of the shop.
A flight attendant said the plane was vibrating so much that she presumed the captain was going to declare an an emergency, but he did not do so.
Do so occasionally refers forwards to a verbal group in the same sentence.
If patients wish to do so, they can buy their own needles and bring them to the acupuncturist to use for their own treatment.