S Corp Is a Tax Status, Not a Structure
The EIN application asks about your legal structure, and an S corp election does not change it. If you formed an LLC with your state, you are an LLC before the election and you are still an LLC after it; Form 2553 only changes how the IRS taxes the entity. So on Form SS-4 or the online EIN assistant, choose Limited Liability Company, enter your state and number of members, and let the application then ask how you want the entity classified for tax purposes. That is where the S corporation option belongs.
Picking Corporation as the legal structure because you are becoming an S corp is the single most common mistake on this form. It tells the IRS you are a state-law corporation, which you are not, and mismatched records make the 2553 election and your first return messier than they need to be.
The Date Questions
Date business started. Use the date your LLC was formed with the state, or the date you actually began operating if you ran the business before forming the LLC. Do not use the S corp election date; the election creates no new business, it re-labels an existing one.
First date wages or annuities were paid. This means real payroll wages. If you have never run payroll, enter the date you expect your first payroll run as an S corp, typically shortly after the election takes effect. This date matters because the IRS uses it to know when to start expecting Form 941 filings from you; a date earlier than your real first payroll invites notices about missing quarterly returns.
If Your LLC Already Has an EIN
An existing single-member LLC electing S corp treatment generally keeps its EIN; you do not apply again. The election rides on the EIN you already have. You only need a new EIN in situations like forming a brand-new entity or an actual state-law incorporation of what used to be an LLC.
The Order of Operations
Form the LLC with your state, get the EIN as an LLC, then file Form 2553 to elect S corp treatment (signed by all owners, with the effective date you want). The IRS mails an acceptance letter, CP261, usually within about 60 days. Keep it with the CP575 EIN letter; between them they answer nearly every onboarding form a bank or payroll provider will ever send you.