If the company was organized, in a specific state, and hires employees, it will need both a Federal and a state tax ID. In other cases, it is simply a sales tax id, used to report sales taxes collected for the state. In any case, it is an IS issued to the company for the purpose of collecting, paying and reporting taxes. That tax id would also be provided to suppliers, in order for them not to charge tax to the company for their purchases.
Individual taxpayers will use their social security number as a tax id, in order to report their own income and pay their own taxes. Small businesses without employees may use their owner's SSN for this same purpose, bowever, many will elect to obtain a tax id in order to separate personal from business tax reporting.
For state income tax returns it is your Social Security Number. They also assign a tax account number to head off identity theft problems.
It's like a social security number for a company.
for an individual, their SSN
for a company, a corporation or a partnership, the company would have applied to Calif for a number like the federal EIN
Each company has its own number.
Are you referring to an individual or a corporation or some other form of business? Could you be a tad more