IRS TIN Matching for Bookkeepers: Free...

IRS TIN Matching for Bookkeepers: Free December Check That Prevents B-Notices

Every January, bookkeepers submit 1099s and hope the vendor TINs on file are correct. Most years they find out they weren't in March, when the CP2100 lands.

There's a better way. The IRS TIN Matching Program at irs.gov/tin-matching is free, available year-round, and built specifically for 1099 filers. Run it in December against your prior 11 months of vendor payments. Fix the mismatches. File clean in January.

That single step is the most common reason bookkeepers stop getting B-Notices.

What is IRS TIN Matching?

IRS TIN Matching is a free online program that lets authorized 1099 filers verify that a vendor's name and taxpayer identification number (TIN) match IRS records before filing. Available at irs.gov/tin-matching, it has two modes: interactive matching (up to 25 name/TIN pairs at a time, instant results) and bulk matching (CSV upload, 24-hour response). Mismatches return a numeric code: 0 means match, 1 means no match, 2 means multiple matches (treat as no-match), 3 means invalid TIN, 4 means deactivated EIN, and 5 means duplicate request. You must be an authorized e-Services user with the TIN Matching Application approved before you can access it.

Key Takeaways

TIN Matching is free - Access at irs.gov/tin-matching; no third-party service needed
Two modes - Interactive matching handles up to 25 pairs instantly; bulk CSV returns results within 24 hours
Six result codes - Code 0 = match, codes 1-4 = mismatches requiring action, code 5 = duplicate request
December is the right month - Run it against 11 months of vendor payments before your January batch filing
Skipping it is the #1 cause of CP2100 B-Notices - Both CP2100 (250+ mismatches) and CP2100A (fewer) trigger a 30-day written solicitation requirement
Registration required - You need an IRS e-Services account with the TIN Matching Application approved before your first run

The 1099 filing workflow for 2026 has several high-impact steps. TIN matching in December is the highest-ROI one. It takes 30 minutes and prevents weeks of B-Notice cleanup. Key terms like TIN, EIN, and backup withholding are defined in the bookkeeping glossary if you need a quick reference.

Why Most Firms Skip It (and What It Costs Them)

The TIN Matching Program has existed since 2003. Awareness is the problem, not access.

Most bookkeepers trust the W-9 on file and assume the TIN is right. The IRS tool is free, accurate (it queries the same database that processes your 1099s), and available 24 hours a day.

When firms skip TIN matching, they get CP2100 or CP2100A notices. CP2100 goes to payers with 250 or more mismatched returns in a year. CP2100A covers fewer mismatches. Both trigger a 30-day window to send written B-Notice solicitations to every flagged vendor, asking them to correct their TIN on a new W-9.

That solicitation has to be in writing and on file. Phone calls don't count.

Running TIN matching in December catches mismatches before the 1099 goes out. No notice. No solicitation. No documentation scramble.

How to Register for the TIN Matching Program

Registration happens through IRS e-Services at irs.gov. Two steps.

Step 1: Create an IRS e-Services account. You'll need a valid SSN or EIN, a US-based phone number, and a financial account number for identity proofing. The IRS uses ID.me, so have a government-issued ID ready.

Step 2: Apply for the TIN Matching Application. Inside e-Services, request access to the TIN Matching Application. Approval typically takes a few days.

One note: TIN Matching is for authorized 1099 filers only, not general research. If you're acting on behalf of bookkeeping clients, apply under your own EIN as a tax professional.

Interactive Matching vs. Bulk Matching

Once registered, you have two options.

Interactive matching handles up to 25 name/TIN pairs at a time, with instant results. Enter the payee name exactly as it appears in Box 1 of the W-9 (individual name for sole proprietors, not the business name in Box 2) plus the SSN or EIN. Results are immediate.

Bulk matching handles larger lists. Upload a CSV with one row per vendor (payee name, TIN type, TIN digits) and get results within 24 hours. Use this for clients with large contractor bases in construction, staffing, or event production.

For a typical practice with 15-25 clients, interactive matching covers most scenarios. Switch to bulk when a single client's December list runs into the hundreds.

Reading the Match Codes

The TIN Matching system returns one of six codes for each name/TIN pair:

Code 0 (Match). The name and TIN match IRS records. You're good to file.

Code 1 (No Match). The name/TIN combination doesn't match. Compare it character by character against the W-9. Common causes: middle initial not on the IRS record, business name used instead of individual name for a sole proprietor, or a TIN with a transposed digit. Request a corrected W-9 and re-run. If the vendor doesn't respond before your filing deadline, you may need to apply backup withholding at 24%.

Code 2 (Multiple Matches, Treat as No Match). Rare, but the IRS guidance is clear: treat it the same as code 1. Request a corrected W-9.

Code 3 (Invalid TIN). Wrong digit count, invalid EIN prefix, or ITIN format mismatch. Almost always a data-entry error. Verify against the W-9 document before contacting the vendor.

Code 4 (Deactivated EIN). The EIN exists but the IRS deactivated it, typically when a business closed. Request a new W-9 immediately.

Code 5 (Duplicate Request). Same name/TIN submitted twice in one session. Check your CSV for repeated rows.

Keep a log of all code 1-4 results: vendor name, TIN submitted, correction taken. If a CP2100 arrives later, that log is your documentation.

The December Workflow

Here's the practical sequence. Run it once a year, in December, against the full year's vendor payment activity.

Pull your 1099-eligible vendor list. Export all vendors paid more than $2,000 in non-credit-card, non-employee payments during the year. Exclude corporations (unless attorneys or healthcare providers), vendors paid exclusively by credit card, and vendors with W-8 forms on file (foreign vendor rules differ; see the 1042-S and foreign vendor guide for those).

Cross-reference W-9s on file. Before you run matching, confirm you have a W-9 for every vendor on the list. Missing W-9s are a separate problem. Start with collecting the W-9 from the vendor before you can run a match.

Run TIN Matching. Interactive for lists under 25; bulk CSV for longer lists. Use the name exactly as the vendor wrote it on their W-9.

Resolve code 1-4 results. Contact vendors with mismatches. Give them two weeks to respond with a corrected W-9. Document every contact in writing.

Re-run matching on corrected TINs. After you receive corrected W-9s, run a second pass to confirm the new name/TIN pairs return code 0.

File your 1099s in January with clean data. The 1099 corrections process is significantly simpler when you're correcting data errors you caught yourself rather than responding to IRS notices.

What Happens If You Skip It

The IRS compares filed 1099s against its records. Mismatches trigger CP2100 or CP2100A notices to the payer. You then have 15 business days to send written B-Notice solicitations to each flagged vendor.

First B-Notice: send the vendor IRS Publication 1281 and request a corrected W-9. Second B-Notice within three years: tell the vendor they must resolve the discrepancy with the Social Security Administration before you can accept a new W-9.

Skip the solicitation, lose the safe harbor. The IRS can then assess 24% backup withholding as your liability. That's the payer's obligation if not properly withheld, not the vendor's.

Running TIN matching in December means none of that happens.

How Growthy Tracks Vendor TINs Year-Round

Built by a CPA firm partner who still reconciles books for real clients, Growthy keeps a continuous vendor record that includes W-9 status, entity type, and TIN on file. When you run your December TIN matching, you're working from a current, reconciled vendor list rather than hunting across spreadsheets and scanned W-9 PDFs.

Growthy categorizes automatically based on pattern learning from your prior corrections. On returning books, categorization accuracy reaches 90%+ after 30 days. On first import, it hits 85%. That accuracy extends to vendor classification: the system flags new vendors who hit the $2,000 threshold before year-end so you can request a W-9 before December rather than during it.

The 1099 workflow features in Growthy also track which vendors have W-9s on file and which are outstanding, so your December TIN matching run starts with a complete, verified list instead of a best-guess export.

FAQ

Do I need a separate IRS e-Services account for each client?

No. You register once under your own EIN as a tax professional. You can run TIN matching for multiple clients from the same account. Keep your client's vendor lists separate in your own records so you can tie match results back to the right client.

Can I use TIN Matching for vendors I already filed 1099s on?

Yes, but it's most useful as a pre-filing step. If you already filed and got a CP2100, TIN matching can help you confirm corrected TINs before you file 1099 corrections. It won't undo the mismatch flag on the original filing, but it confirms the corrected data before you resubmit.

What if the vendor insists their TIN is correct but I still get a code 1?

Run the name/TIN exactly as it appears on the IRS-issued document (SS-4 confirmation letter for an EIN, Social Security card for an SSN). If you still get code 1, the mismatch is real. The vendor needs to contact the IRS or SSA to resolve the discrepancy. Document that you ran matching and that you notified the vendor. That documentation is your protection if the IRS later questions the filing.

Is TIN Matching only for 1099-NEC, or does it cover all 1099 types?

The TIN Matching Program covers all information returns that report TINs: 1099-NEC, 1099-MISC, 1099-INT, 1099-DIV, 1099-B, 1099-R, and others. For most bookkeepers, the relevant forms are 1099-NEC and 1099-MISC. See 1099-NEC vs. 1099-MISC for which form applies to which payment type.

What's the difference between a B-Notice and a CP2100?

CP2100 and CP2100A are the IRS notices that tell you there were name/TIN mismatches on your filed returns. A B-Notice is what you send to the vendor in response. The IRS doesn't send B-Notices; you do. The B-Notice solicitation to the vendor is what triggers the 30-day correction window and preserves your safe harbor from backup withholding liability. The terms are often used interchangeably in practice, but technically the CP2100 is what you receive and the B-Notice is what you send.

Get started with Growthy and keep your vendor TIN records current year-round, so your December TIN matching run takes 30 minutes instead of 3 hours.

Tax figures verified against IRS Notice 2025-62, IRS 1099-K FAQs, §3406 proposed regulations, and IRS Pub 1099 General Instructions on 2026-05-14.