When the IRS Thinks You're Two Companies: A Duplicate EIN Case Study

Most tax problems come from something a business did — a missed deadline, an incorrect election, an overlooked filing. But sometimes the problem isn't caused by the business at all. It's caused by an administrative error that happened years earlier, quietly compounding in IRS records until it finally surfaces as a real headache.

That's exactly what happened with one of our clients, and it took nearly a year working through the IRS Taxpayer Advocate Service to fix.

How It Started

The client had formed a single-member LLC and was issued an Employer Identification Number (EIN) at formation — completely standard. The following year, the business elected to be taxed as an S-Corporation by filing Form 2553. This is a common and straightforward move for a small LLC: the entity doesn't change its legal form, it simply elects a different tax treatment. Critically, electing S-Corp status does not require a new EIN. The existing EIN carries forward.

Somewhere in that election process, however, the client's prior accountant mistakenly obtained a second EIN for the same business. From that point forward, the company filed all of its federal returns — Form 1120-S, payroll filings, everything — under the new EIN. The original EIN sat dormant in IRS systems, technically still associated with the business, but with no filing history attached to it going forward.

For years, this caused no visible problem. The business filed consistently, on time, under one EIN. But underneath the surface, the IRS's records showed two EINs tied to the same entity — with no clear link between them, and no clean way for the system to recognize that they represented one continuous taxpayer rather than two separate companies.

When It Became a Real Problem

The client came to our firm years after all of this had already happened, with no reason to think there was anything unusual in their EIN history. The issue only came to light when we attempted to e-file the company's Form 1120-S and the filing was rejected. E-file rejections tied to entity information are usually simple fixes — a typo, a mismatched name control. This one wasn't.

When we dug into why the rejection was happening, that's when we discovered the business had two EINs on file with the IRS for over 10 years: the original one issued at formation, and a second one obtained during the prior accountant's handling of the S-Corp election years earlier. The rejection was the IRS system's way of flagging that something in its records didn't line up — in this case, an S-Corp election and years of 1120-S filing history that weren't cleanly tied to a single, unambiguous EIN. Untangling which EIN "owned" the S-Corp election, and which one the IRS should treat as the operative account going forward, became a genuine administrative snarl.

This is the kind of problem that doesn't resolve itself through normal channels. Standard IRS correspondence lines are built for individual notice disputes, not for merging two EIN records that both technically belong to the same legal entity. So we escalated the case to the IRS Taxpayer Advocate Service (TAS) — the independent office within the IRS designed to help taxpayers who are experiencing significant hardship or whose issue isn't getting resolved through normal channels.

The Resolution Path

Working with the Taxpayer Advocate on this case took approximately twelve months from start to finish. That's a long time, but it reflects the reality of untangling a records issue that spans multiple years and touches several IRS systems that don't always talk to each other cleanly.

A key piece of the resolution was a signed affidavit from the client, laying out — under penalty of perjury — the full timeline: when the LLC was formed, when the S-Corp election was made, how the second EIN came to be issued in error, and an explicit request that the IRS:

• Recognize both EINs as belonging to the same legal entity
  
• Merge the historical record from the original, unused EIN into the EIN actually used for filings
  
• Confirm the S-Corp election's effective date under the correct, active EIN
  
• Deactivate the unused EIN going forward to prevent any future confusion
  

This kind of sworn statement gives the Taxpayer Advocate something concrete and authoritative to work from when coordinating internally with IRS records units — it's not just a phone call explaining the situation, it's a documented, client-attested account the advocate can attach directly to the case file.

What This Case Illustrates

A few takeaways worth keeping in mind, whether you're a business owner or a fellow practitioner:

A duplicate EIN is more common than you'd think. It tends to happen during transitions — entity elections, ownership changes, or when a prior bookkeeper or accountant unfamiliar with the entity's full history requests a new number "just in case." When in doubt about whether a change in tax election requires a new EIN, the answer is almost always no.

These issues rarely surface immediately, and they often surface as something else entirely. In this case, years passed with no visible problem, and the first sign of trouble wasn't a notice about EINs at all — it was a routine e-file rejection on the current year's return. A new advisor picking up a client's filings is often the first to notice these legacy inconsistencies, simply because they're the first to look closely at the entity's full IRS history rather than just continuing what the prior preparer had been doing.

The Taxpayer Advocate Service exists for exactly this kind of case. If you've tried resolving an IRS issue through standard correspondence and you're not getting anywhere — especially on something structural like a records mismatch rather than a simple notice dispute — TAS is worth pursuing. It's a free, independent resource within the IRS itself.

Patience and documentation are the price of admission. A year is a realistic timeline for this type of structural correction. Going in with a clear, well-documented timeline (and a sworn affidavit when appropriate) is what allows the advocate to actually move the case forward rather than getting stuck in the same loop that caused the problem in the first place.

If your business has received confusing IRS correspondence tied to an EIN you don't recognize or no longer use, don't ignore it — these issues tend to compound the longer they sit. The Accountancy's tax team can help you determine whether you're dealing with a simple notice or a deeper records issue.

‍