S-corporations, like LLCs, aren’t generally required to have tax ID numbers. Instead, it’s based on a few factors. A tax ID number will be required if the S-corporation has more than a single owner. A tax ID number will also be required if the S-corporation has any employees, though the owner of the company will not count as an employee.
An S-corporation can use tax ID numbers to purchase goods wholesale, pay taxes, and acquire licenses and permits. Most S-corporations will eventually find themselves having to request a tax ID number, even if it’s only to sign a business lease, or open a business bank account. A very simple S-corporation with a single owner and no employees may not need to.
Tax ID numbers are used for a number of financial and tax-related documents, and while some S-corporations can use an owner’s SSN for this, it’s often not advised. Having a tax ID number makes for a cleaner barrier between the owner’s own accounts and the S-corporations accounts, though taxes are passed through.