When does a small business need to register for PF and ESI?

PF registration is generally mandatory once an establishment has 20 or more employees; below that, it can be taken voluntarily. ESI generally applies to establishments with 10 or more employees (the threshold can differ by state), covering employees earning up to the prescribed monthly wage ceiling.

Contributions start from the date the establishment becomes covered. Since coverage depends on your state and the nature of your business, confirm the exact position with your CA or the EPFO and ESIC offices.