Whether you need a new EIN when converting an LLC to a C corp depends on how your LLC was taxed the day before the conversion. If it was taxed under the default rules as a disregarded entity or a partnership, the IRS treats the conversion as the creation of a new taxable entity, and you need a new EIN. If your LLC had already elected corporate tax treatment by filing Form 8832, the tax classification isn’t actually changing, and you keep the EIN you already have.
When a New EIN Is Required
Most conversions fall into this category. A single-member LLC is treated as a disregarded entity for income tax purposes, and a multi-member LLC is treated as a partnership.1Internal Revenue Service. LLC Filing as a Corporation or Partnership When either type becomes a C corporation, the IRS views it as the formation of a new taxable entity rather than a continuation of the old one.
The IRS says this directly in two places. Under its LLC guidance, a new EIN is required when you “terminate an existing LLC and form a new corporation.” Under its partnership guidance, a new EIN is required when you “incorporate.”2Internal Revenue Service. When to Get a New EIN A multi-member LLC defaults to partnership treatment, so incorporating it falls squarely under the partnership rule. The same logic covers a single-member LLC moving from disregarded-entity status to filing a full corporate return.
The requirement applies whether you convert through a statutory conversion under state law or dissolve the LLC and form a new corporation. What matters for federal tax purposes is the change in classification, not the state-law mechanics.
When You Can Keep Your Existing EIN
You avoid needing a new EIN if the LLC was already being taxed as a corporation before the legal conversion. An LLC can elect corporate tax treatment at any time by filing Form 8832, Entity Classification Election.3Internal Revenue Service. About Form 8832, Entity Classification Election Changing your tax election alone does not require a new EIN.2Internal Revenue Service. When to Get a New EIN
The Form 8832 instructions make it explicit: “Any entity that has an EIN will retain that EIN even if its federal tax classification changes.” The form also cautions filers not to apply for a new EIN when an existing entity is simply changing classification.4Internal Revenue Service. Form 8832, Entity Classification Election Once the IRS already recognizes your LLC as a corporation for tax purposes, a subsequent state-level conversion into a formal C corporation doesn’t change the tax structure in a way that triggers a new EIN.2Internal Revenue Service. When to Get a New EIN
Some owners use this sequence deliberately: file Form 8832 first, then convert at the state level. Keeping the same EIN preserves the tie to your existing IRS account, tax history, bank accounts, and vendor records.
How to Get the New EIN
If your conversion does require a new EIN, the fastest route is the IRS online application. It’s free, takes about 15 minutes, and the number is issued immediately upon approval. The online tool is available Monday through Friday from 6:00 a.m. to 1:00 a.m. Eastern, Saturday from 6:00 a.m. to 9:00 p.m., and Sunday from 6:00 p.m. to midnight. You can’t save your progress, so have the corporation’s details ready before you start.5Internal Revenue Service. Get an Employer Identification Number
You can also apply by mailing or faxing Form SS-4. Faxed applications are typically processed within four business days, and mailed applications take four to five weeks. Print and keep the confirmation notice. You’ll need the new EIN for the corporation’s first tax return, payroll registrations, and updated bank accounts.
Tax Returns During the Transition Year
A mid-year conversion splits your filing obligations. The old entity files a final return, and the new corporation files its first return, each covering part of the year.
Final Return for the LLC
If your multi-member LLC was taxed as a partnership, file a final Form 1065 covering the period from the start of the tax year through the day before the conversion takes effect. The return is due on the 15th day of the third month after that short period ends.6Internal Revenue Service. 2025 Instructions for Form 1065 For a single-member LLC, the owner reports the LLC’s income on their individual return, typically on Schedule C, through the conversion date.
Mark the final return box on whichever form applies. That tells the IRS not to expect further returns under the old classification.
First Return for the C Corporation
The new C corporation files Form 1120 for the short period running from the conversion date through the end of its tax year. A new corporation filing a short-period return must generally file by the 15th day of the fourth month after the short period ends.7Internal Revenue Service. Instructions for Form 1120 (2025) Convert on July 1 with a calendar tax year, and the short period runs July 1 through December 31, with Form 1120 due by April 15 of the following year.
Income, deductions, and credits have to be allocated between the two returns. Get the allocation wrong and you risk underreporting on one and overreporting on the other, which can trigger matching notices on both.
Payroll and Employment Tax Consequences
If your LLC had employees, the EIN change creates extra payroll paperwork. File final employment tax returns under the old EIN through the conversion date, including Form 941 for quarterly wages and Form 940 for federal unemployment tax. The new corporation then starts its own payroll tax reporting under the new EIN from the conversion date forward.8Internal Revenue Service. Assigning Employer Identification Numbers (EINs)
This split affects wage-base calculations. Social Security tax has an annual wage base, and when a new EIN starts fresh, the system doesn’t automatically carry over what each employee has already earned that year. Without proper tracking, you can overwithhold Social Security tax. Make sure your payroll provider knows the conversion date and carries year-to-date wage information forward internally, even though each EIN’s filings will show only its own portion of the year.
Notifying the IRS of the Conversion
Beyond the new EIN and the split returns, you may need to update the IRS on other changes.
Business Name Change
If you’re filing a Form 1120 for the current year, check the name change box on page 1, line E, box 3. If you’ve already filed this year’s return before the name changed, write to the IRS at the address where you filed. A corporate officer must sign the letter.9Internal Revenue Service. Business Name Change
Responsible Party or Address Change
If the conversion changes who the IRS considers the entity’s “responsible party” (the person who controls or manages the entity and its funds), file Form 8822-B within 60 days of the change.10Internal Revenue Service. Form 8822-B, Change of Address or Responsible Party – Business The same form handles business address changes. This matters when you’re keeping your EIN; if you obtained a new one, the responsible party information was captured during that application.
Keeping the Switch Clean
The biggest mistake owners make is treating the EIN question as an afterthought. If you want to avoid a new EIN, plan before the conversion, not after. Filing Form 8832 to elect corporate tax treatment ahead of the state-level conversion preserves the EIN and keeps your IRS account, payroll records, and bank accounts intact.
If you do need a new EIN, work through these steps in order:
- Apply for the new EIN on or before the conversion date. You can’t file the corporation’s first return or set up payroll without it.
- Notify your bank right away. Some banks update the EIN on the existing account; others require closing the old account and opening a new one.
- Update state registrations, including your state tax authority, unemployment insurance account, and any professional licenses tied to the old EIN. State timelines vary.
- Tell vendors and clients. Anyone issuing a 1099 for payments to your business needs the new EIN to report accurately.
- File final returns under the old EIN, including employment tax returns, and mark each one as final so the IRS closes out the old account.
The conversion is a one-time event. Sloppy EIN handling generates paperwork that follows you for years.