All about TIN/SSN verification at year-end

Verifying Taxpayer Identification Numbers (TINs) and Social Security Numbers (SSNs) is a foundational step for accurate reporting and risk management. Before you file tax year 2026 forms in early 2027, confirm that every identifier is correct for your employees, vendors, and contractors. That helps you avoid penalties, backup withholding, and operational disruptions.

This guide will strengthen your compliance with a deep dive into the TIN and SSN verification process.

Why TIN and SSN verification matters

Accurate TIN and SSN verification is vital for successful year-end reporting and compliance. It plays a key role when preparing forms such as the 1099 series for independent contractors and vendors, as well as the W-2 for employees. Ensuring that these identifiers are correct reduces risk for both your business and your payees.

Types of taxpayer identification numbers

• Social Security Number (SSN): Used for individual tax reporting, work authorization, and government benefits
• Employer Identification Number (EIN): Identifies businesses for federal tax purposes
• Individual Taxpayer Identification Number (ITIN): Issued to certain nonresident and resident aliens, their spouses, and dependents who cannot obtain an SSN. Don't accept an ITIN in place of an SSN for Form W-2 reporting, per the IRS instructions for Forms W-2 and W-3.

For more details, see IRS: Taxpayer Identification Numbers.

Consequences of incorrect TINs

Providing correct TINs and SSNs benefits employees, vendors, and contractors by supporting smooth and timely year-end filing. Inaccurate data introduces several risks.

Incorrect TINs on 1099 forms

• Request a TIN from each payee before you pay them. The IRS suggests using Form W-9 to collect it, per Publication 1099.
• If a payee's name and TIN don't match IRS records, the IRS sends you a CP2100 or CP2100A notice. You then have 15 business days to send the payee a "B" notice and a new Form W-9. See IRS Publication 1281.
• If the payee doesn't provide a corrected TIN in time, you must begin backup withholding, where you withhold 24% of eligible payments and remit them to the IRS.
• For payments made after 2025, the threshold for reporting most nonemployee payments and backup withholding on them rose from $600 to $2,000. If you backup withhold, you report the payment on a 1099 regardless of the amount.
• Unresolved mismatches can also lead to the penalties described below and increased scrutiny.

For additional information, review the IRS: Backup Withholding B Program.

Incorrect SSNs on W-2 forms

• During hiring, employees must provide their SSN to the employer.
• Incorrect or missing SSNs at year-end can delay tax return processing, impact refund timing, and affect the employee's Social Security earnings record. The SSA uses the SSNs on Form W-2 to record earnings for future benefits.

Verifying TINs and SSNs prior to filing demonstrates due diligence and protects all parties from avoidable errors, notices, and withheld payments.

Penalties to the business

Accurate TIN and SSN verification is essential to avoid costly IRS penalties. For returns required to be filed in 2027, which covers tax year 2026 forms, the penalties for information returns with incorrect or missing TINs are:

A small business has average annual gross receipts of $5 million or less over the three most recent years. These amounts come from Rev. Proc. 2025-32. The IRS charges separate penalties for failing to file a correct return and for failing to furnish a correct payee statement.

For most returns, intentional disregard of the filing requirements carries a penalty of the greater of $690 per return or 10% of the amount required to be reported, with no maximum. You may avoid a penalty if you can show reasonable cause. IRS Publication 1586 explains the requirements for missing and incorrect names and TINs. See IRS: Information Return Penalties for current details.

Taking proactive steps to verify TINs and SSNs is an effective way to reduce your organization's risk and support efficient, accurate year-end reporting.

How to verify TINs and SSNs, step by step

A methodical approach ensures compliance and reduces end-of-year strain. The following steps offer a clear path for both TIN and SSN verification using official IRS and SSA resources.

Step 1: Collect and document data

For vendors and contractors

• Use IRS Form W-9 to capture the payee's legal name, correct TIN (SSN, EIN, or ITIN), and a certified signature
• Make W-9 collection a mandatory part of onboarding before issuing any payment to minimize year-end filing delays

For employees

• Use IRS Form W-4 to collect each employee's Social Security Number (SSN). USCIS Form I-9 verifies identity and work authorization, and the SSN field on Form I-9 is optional unless you use E-Verify
• Ensure employees provide their legal name exactly as it appears on their Social Security card to prevent mismatch notifications from the SSA

For further reading: The Complete Guide to I-9 & E-Verify

Step 2: Register for verification services

TIN matching

• Create an IRS account, then complete the TIN Matching application in IRS e-Services. See the IRS TIN Matching page for the application link and account help
• TIN Matching is only for payers and their authorized agents that submit information returns. A payer must be listed in the IRS Payer Account File, which includes payers that filed Forms 1099 within the last two years
• Complete the TIN Matching application and be added as an authorized user
• Refer to IRS Publication 2108 for program details

SSN verification

• Register via SSA Business Services Online (BSO), using either Login.gov or ID.me
• After credentialing, request access to the Social Security Number Verification Service (SSNVS)
• An activation code will be mailed to your employer. Enter this code to activate your SSNVS access

Step 3: Use the official matching tools

TIN matching

Once your account is active:

• Access the IRS TIN Matching tool
• Use Interactive TIN Matching to verify up to 25 name/TIN pairs at a time with results in real time, which suits new or small batch verifications
• For high volumes, use Bulk TIN Matching to upload files of up to 100,000 name/TIN combinations. Results are returned within 24 hours. See the IRS TIN Matching tutorial (PDF)
• The system provides a code for each entry. Follow up immediately on any mismatches
• TIN Matching is for payees on Forms 1099. Use SSNVS for W-2 employees

SSN matching: Social Security number verification service (SSNVS)

• Offered through SSA's BSO, the SSNVS system allows verification of names and SSNs prior to filing Forms W-2
• Employers may:
  • Verify up to 10 names and SSNs instantly through an online form, which is ideal for new hires
  • Upload files containing up to 250,000 names and SSNs, with results usually available the next government business day, which is useful for payroll database reviews
• SSNVS can only be used to verify current and former employees for wage reporting

For more information, check out SSA: Social Security Number Verification.

Best practices to streamline year-end TIN and SSN verification

Strong verification policies minimize year-end challenges and reduce compliance risk. Implement the following practices:

• Standardize information collection: Require a completed, signed W-4 for every employee and a W-9 for every vendor or contractor before processing payments. Consider integrating digital collection tools to automate requests and storage.
• Year-round SSN and TIN verification: Verify identifiers as you onboard new employees and vendors. Consistent, incremental verification reduces the year-end workload and addresses discrepancies as they arise.
• Prompt communication: Address mismatches quickly. If a verification check fails, notify the employee or contractor, explain the issue, and request an updated W-4 or W-9.
• Maintain organized records: Document all verification activities. Retain copies of W-4s and W-9s, and log all actions, including dates, system outputs, and related correspondence. Good recordkeeping demonstrates due diligence during any IRS review. See why year-end form archiving protects your business.

How Greenshades supports year-end verification

TIN and SSN verification is a vital step in the year-end process. Greenshades simplifies this task by integrating it directly into the Year-End Forms wizard.

The process involves these steps:

• Upload your data and start the verification process
• Receive results within three business days
• Follow up on any TINs or SSNs flagged as invalid and update records as needed

Generally, the portal opens for data verification in December of each tax year. Once available, you can verify TINs for 1099s and SSNs for W-2s and 1095s. Integrating verification into your workflow helps prevent last-minute issues, streamlines compliance, and reduces administrative tasks as you close out the year.

Secure your organization for a smooth tax season

TIN and SSN verification is a critical part of year-end compliance and should be integrated into routine processes. By leveraging IRS and SSA resources, establishing strong data collection and verification practices, and using tools like Greenshades to automate key steps, you ensure your organization avoids costly errors and penalties.

Review your procedures now, close gaps, and position your business for a smooth and compliant tax season. For the full filing sequence, see our W-2 and 1099 filing checklist.