It is just to the right of the OH. It might be in a format like 52-xxxxxxx or something similar.
**Mark the post that answers your question by clicking on "Mark as Best Answer"
If it's blank, and there's an amount in box 17, you will have to contact your employer to get that. Or you could try entering the federal EIN there. If boxes 16 & 17 are blank. you don't need the employer's state ID