Ask the Taxman- What kind of paperwork do you need to submit if your LLC has no activity in a year?
Source: Quora
Answer:
That would depend on how you elected to file. If you elected to file as an entity (C Corp, S Corp, Partnership), your will need to file an entity return by March 15th, 2022.
If you are considered a sole proprietorship, technically you do not have to list the business if you have no income but you probably should include a Schedule C on your personal return. Since you said you had no activity, you likely have a tax loss (benefit).
Also, since you said you had no activity, make sure you understand the profit motive rules regarding your activity, so the IRS does not consider it a hobby.