In Fiscal Year 2024, the IRS opened 639,143 new taxpayer delinquency investigations. In Fiscal Year 2025, that number skyrocketed to 2,501,667. That’s an increase of approximately 291%, nearly four times as many investigations in just one year.

A taxpayer delinquency investigation, commonly referred to as a TDI, is generally initiated when the IRS believes a taxpayer was required to file a tax return but failed to do so.

In simple terms, this is usually a non-filer issue.

This is different from a taxpayer delinquent account, which typically involves a filed return and an outstanding balance due. A TDI focuses on the missing tax return itself.

Why This Matters

For tax resolution professionals, non-filer cases often signal the beginning of a much larger problem.

Many taxpayers believe their issue is simply unpaid taxes. However, after reviewing IRS account transcripts, it often becomes clear that the real issue involves multiple years of unfiled tax returns.

Until those missing tax returns are filed, many IRS resolution options may be unavailable. The IRS generally requires taxpayers to become compliant before it will seriously consider:

• Installment Agreements
• Currently Not Collectible (CNC) Status
• Offers in Compromise (OIC)
• Other long-term resolution programs

The IRS Inventory Is Growing Too

The IRS Data Book also revealed that the agency ended FY 2025 with 3,234,815 taxpayer delinquency investigations in inventory, up from 2,050,877 just one year earlier.

This was not simply a temporary spike in new investigations.

The number of open investigations grew substantially as well, indicating that non-filer enforcement continues to be a significant area of IRS focus.

Final Takeaway

The takeaway is simple: non-filer investigations are not going away.

Based on these numbers, taxpayer delinquency investigations appear to be becoming a much larger part of the IRS collection landscape.

This is also one of the areas where artificial intelligence is likely to have a major impact. As technology continues to evolve, the IRS will have increasingly sophisticated tools to identify missing returns, prioritize enforcement activity, and automate portions of the compliance process.

If you’re behind on filing your tax returns or have received notices from the IRS regarding unfiled returns, now is the time to take action.

At Munoz & Company, CPA, we help taxpayers resolve unfiled return issues, regain filing compliance, and navigate complex IRS problems. Whether you need assistance filing past-due tax returns, negotiating payment arrangements, or exploring other tax resolution options, our experienced team is here to help.

Don’t face the IRS alone. Munoz & Company, CPA is here for YOU. Contact us today to discuss your situation and learn how we can help you take control of your tax matters and work toward a lasting resolution.