Do so (did so / doing so, etc.) is used instead of repeating a verb phrase when it is clear from the context what we’re talking about:
- Can you send these photos to my email address? - I've already done so.
He asked me to leave and I did so.
I asked Adeline whether she intended to apply for the master's programme and she said she had no plans to do so.
Do so is most often used in formal spoken or written English. To sound less formal, we can use do it or do that:
We’d bought the tickets three months prior to the beginning of our trip. We did it / did that because the prices tend to increase closer to the departure date.
We can also omit “so” in less formal English, especially after modals or perfect tenses:
- Will this program work on my computer if I update it? - It should do.
- Could you have gone to Japan instead? - Yes, I could have done it.
We use do so instead of verbs that describe actions, but we avoid adding “so” when replacing verb phrases that describe states and habitual actions:
19% of residents voted before the scheduled election day this year, while only 14% did so last year.
If you want to lose weight, you should only do so without resorting to extreme dieting.
Anyone wishing to ask a question should feel free to do so.
States / habitual actions
He complains a lot more than I do.
I don’t have time to go to the gym today, but I usually do.
Madeline doesn’t like amusement parks but Kate does.
We can use such + (a / an) + noun to refer back to something mentioned before, with the meaning ‘of this / that kind’. We use such + noun when the noun is uncountable or plural, and such + a / an + noun when the noun is countable and singular. Such is used in this way mainly in formal speech and writing:
Tom was screaming and running around the classroom during the lesson. Such behaviour was clearly inappropriate.
The company has finally published a report on its income and expenditures. Such reports are prepared on a yearly basis.
Nicole is pretty tough and sharp-tongued. No wonder no one wants to befriend such a person.