According to the IRS, all churches should have an employer identification number (EIN) whether or not they have any employees. Each church is responsible for obtaining its own EIN. There are many instances in which an EIN is necessary. For example, a church needs an EIN when it opens a bank account, in order to be listed as a subordinate in a group ruling, or if it files returns with the IRS (e.g., Forms W-2, 1099, 990-T).
Here is a link to the IRS website that answers many questions regarding the EIN, including how to apply and how to recover it if it’s been lost.