Every tax return processed by the IRS is tagged with a hidden identifier that most taxpayers never notice—but IRS systems rely on constantly. That identifier is the Document Locator Number, commonly referred to as the DLN.

Understanding the IRS Document Locator Number DLN can help explain where your return is being processed, which IRS service center controls it, and how the IRS finds your return if it is pulled for review.

What Is an IRS Document Locator Number (DLN)?

The Document Locator Number (DLN) is a 14-digit number assigned to every tax document that posts to the IRS Master File.

The DLN acts as:

• A filing “address” inside IRS systems
• A routing identifier for processing pipelines
• A locator for both digital and paper records

Once assigned, the DLN stays with the return throughout its life cycle.

Why the DLN Matters More Than You Think

While taxpayers focus on refund dates and transcript codes, IRS employees rely on the DLN to:

• Identify where a return entered the system
• Determine which service center processed it
• Locate the return during audits, reviews, or corrections

If a return is delayed or pulled for review, the DLN is how the IRS finds it quickly.

Breaking Down the 14 Digits of the DLN

Each section of the DLN has a specific meaning.

1. Service Center Code (First 2 Digits)

The first two digits identify which IRS Service Center originally processed the return.

Examples include:

• 01–09: Legacy service center identifiers
• 10–19 and above: Modernized processing locations

This tells you where your return entered the IRS pipeline.

DLN Service Center Code Table

How to Use This Table

If your DLN begins with:

• 03, 05, 06, 07, 09, or 12 → Your return entered a currently active IRS campus
• 20 → Your return was routed through modernized IMF/CADE2 processing
• 01–14 (legacy) → Your return may have passed through older routing logic or reassigned workloads

This helps explain why two taxpayers who filed on the same day may experience different processing speeds.

Why Service Center Codes Matter During Delays

When a return is:

• Pulled for manual review
• Sent to ERS, IVO, or RIVO
• Adjusted after filing

The service center code determines:

• Which IRS unit owns the case
• Which backlog applies
• Where correspondence originates

This is why IRS agents often reference “the campus” when discussing delays.

2. Tax Class Code (3rd Digit)

This digit identifies the type of tax document.

Common examples:

• 1 = Individual income tax (Form 1040)
• 2 = Business tax
• 3 = Employment tax

3. Document Type (4th–5th Digits)

These digits identify the specific form or return category, such as:

• Original return
• Amended return
• Adjustment or supplemental filing

This helps the IRS distinguish between different filings tied to the same taxpayer.

4. Julian Date (6th–8th Digits)

The Julian date represents the day of the year the return was processed.

For example:

• 032 = February 1
• 120 = April 30

This gives insight into when your return entered active processing.

Julian Date Calendar – 2026

IRS Processing & Transcript Reference

The IRS often uses Julian dates inside systems like DLNs, processing logs, and internal posting schedules. A Julian date represents the day number of the year, from 001 to 365 (2026 is not a leap year).

January 2026

February 2026

March 2026

April 2026

May 2026

June 2026

July 2026

August 2026

September 2026

October 2026

November 2026

December 2026

5. Daily Sequence Number (Last 6 Digits)

The final digits are a unique sequence number assigned that day.

This ensures that:

• No two returns share the same DLN
• Each return can be precisely located

Think of it as the return’s serial number.

Where You Can Find the DLN

The DLN commonly appears on:

• IRS Account Transcripts
• Adjustment notices
• Audit correspondence
• Internal IRS references

It is usually labeled simply as “DLN” or embedded in transcript entries.

How the DLN Is Used During Reviews and Delays

If a return is:

• Pulled for manual review
• Sent to ERS, IVO, or RIVO
• Converted from digital to paper handling

The DLN tells the IRS technician exactly where the return is stored—digitally or physically.

This is why older or paper-related cases often reference DLNs during correspondence.

DLN vs. Transaction Codes: Different Roles

It is important not to confuse DLNs with transaction codes.

• DLN = Identifies the document
• Transaction Codes (TCs) = Describe actions taken on the account

Both appear on transcripts, but they serve entirely different purposes.

What Happens Next?

Once assigned, the DLN is:

• Stamped permanently on the Master File
• Used for all future references to that return

If your return is pulled for review, the DLN allows the IRS to retrieve the correct digital or physical “folder” instantly.

The IRS Document Locator Number DLN is the IRS’s internal GPS for your tax return.

It tells the IRS:

• Where your return came from
• What type of document it is
• When it entered processing
• How to find it during reviews

While most taxpayers never need to act on a DLN, understanding it adds clarity when returns stall or move into manual handling.

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