An ACA data matching issue is a notice from the health insurance marketplace telling you that something on your application doesn’t match what federal databases show, and that you need to submit documents to prove your information is correct. The marketplace checks your application against records at the IRS, the Social Security Administration, and the Department of Homeland Security. When something doesn’t line up, you get a formal notice, a deadline, and a list of documents to send in. You can still enroll and receive advance premium tax credits while you resolve it, but missing the deadline can cost you those credits and leave you with a large tax bill.1Centers for Medicare & Medicaid Services. Resolving Data Matching Issues (DMIs) Job Aid
Why the Marketplace Flags Applications
Federal rules require the marketplace to verify your eligibility before awarding premium tax credits or cost-sharing reductions.2eCFR. 45 CFR 155.315 – Verification Process Related to Eligibility for Enrollment in a QHP Through the Exchange When the automated checks can’t confirm something you entered, the system creates what regulations call an “inconsistency” and what nearly everyone else calls a data matching issue, or DMI. Your eligibility determination notice will describe your eligibility as “temporary.”
Three categories account for most DMIs:
- Income. Your projected household income for the coverage year doesn’t match what the IRS and other income databases show. If you estimate $40,000 and last year’s tax return showed $60,000, that gap is often enough to trigger a flag, even when the drop is real because you changed jobs or reduced your hours. Freelancers, seasonal workers, and people paid on commission see this most often.
- Citizenship or immigration status. The marketplace verifies citizenship through the Social Security Administration and lawful immigration status through the Department of Homeland Security’s SAVE system. A hyphenated name entered differently than it appears in SSA records, a transposed digit in a Social Security number, a recent name change from marriage, or recent naturalization can all cause a mismatch.
- Employer-sponsored coverage. Federal databases show your employer offers a health plan, but you said on your application that you don’t have access to affordable job-based coverage. The marketplace needs verification rather than taking your word for it.3eCFR. 45 CFR 155.320 – Verification Process Related to Eligibility for Insurance Affordability Programs
A DMI is not a denial. Your coverage starts, and any advance premium tax credits you were awarded are paid to your insurer. Those payments are provisional, though. If your information turns out to be wrong, you’ll owe that money back when you file your federal tax return.
How to Check Whether You Have One
The marketplace mails a copy of your eligibility notice, but mail gets lost. The faster way to check is through your HealthCare.gov account. Log in, select “Go to My Applications and Coverage,” and choose your current application. From the left-hand menu, select “Eligibility & appeals,” then “View Eligibility Notice.”4Centers for Medicare & Medicaid Services. Resolving Data Matching Issues The “Application details” screen lists every open DMI in your household, broken down by person and category.
Read the notice carefully. It names the exact piece of information that triggered the issue and the type of documentation the marketplace will accept. Sending the wrong document is one of the most common ways people burn through their resolution window.
Deadlines You Cannot Miss
You have 90 days from the date of the eligibility notice to resolve an income or employer-coverage DMI, and 95 days for a citizenship or immigration DMI.5Centers for Medicare & Medicaid Services. Resolving Data Matching Issues (DMIs) The clock starts five days after the date printed on the notice, unless you can show you received it later.
In prior years, income DMIs came with an automatic 60-day extension, giving consumers 150 days total. That extension has been eliminated for plan year 2026. The 90-day window is now a hard deadline.
If the deadline passes, the marketplace redetermines your eligibility using whatever its trusted data sources show, not what you put on your application. In most cases that means your advance premium tax credits get reduced or terminated. For citizenship or immigration DMIs, coverage itself can end.6Centers for Medicare & Medicaid Services. How to Resolve Income Data Matching Issues (DMIs)
How to Submit Documents
You can upload documents directly through your HealthCare.gov account or send photocopies by mail. Uploading is faster and gives you a confirmation, which matters when you’re working against a deadline.
Uploads must be PDF, JPEG, PNG, GIF, TIFF, BMP, or XML. Each file must be under 10 MB, and file names can’t contain special characters like slashes, colons, asterisks, or quotation marks.7HealthCare.gov. Uploading Documents Phone photos work as long as the text is legible and nothing is cut off at the edges.
To mail documents, send photocopies (never originals) to:
Health Insurance Marketplace
Attn: Coverage Processing
465 Industrial Blvd
London, KY 40750-0001
Include the barcode page from the last page of your eligibility notice. If you don’t have it, write your printed name and application ID on every page. The application ID appears near your mailing address at the top of the notice. Without that identifying information, your documents may never be matched to your application.7HealthCare.gov. Uploading Documents For help with the process you can call 1-800-318-2596 (TTY: 1-855-889-4325), though documents cannot be submitted by phone or email.8HealthCare.gov. Contact Us
What Documents to Send
Your eligibility notice lists the specific documents the marketplace wants for your situation. Start there rather than guessing. As a general guide:
Income
Recent pay stubs covering at least the last month are the most straightforward proof of current earnings. A W-2 from the most recent tax year helps, though it reflects last year’s income rather than your projection. If you’re self-employed, a copy of your most recent Form 1040 or a self-employment ledger showing income and expenses will work.
When your income is genuinely hard to predict and you can’t produce standard documentation, the marketplace accepts an “Annual Income Letter of Explanation.” This is a written statement describing your expected income for the year and why it differs from historical records.9HealthCare.gov. Health Plan Required Documents and Deadlines The marketplace still evaluates whether your explanation is reasonable, but the option exists because not everyone has a steady paycheck to document.
Citizenship or Immigration Status
U.S. citizens can submit a passport, birth certificate, or Certificate of Naturalization. For lawful immigration status, a Permanent Resident Card (I-551), Employment Authorization Document (I-766), or another qualifying immigration document listed on HealthCare.gov will work.10HealthCare.gov. Immigration Documentation Types Documents in a language other than English need a certified English translation with a signed statement from the translator attesting to competency and accuracy.
Employer-Sponsored Coverage
The standard form is the Employer Coverage Tool, a PDF available on HealthCare.gov.11HealthCare.gov. Employer Coverage Tool Give it to your HR department to complete with details about what the plan costs and what it covers. Some employers are slow, so don’t wait until the last week of your window to ask. Information from an employee benefits portal or a letter from your employer describing the plan’s cost and coverage details will also work.12HealthCare.gov. Steps to Decide Between Job-Based or Marketplace Coverage
What a Missed Deadline Costs in 2026
The financial stakes got significantly worse this year. In prior years, if you received more advance premium tax credits than you were entitled to, the amount you had to repay at tax time was capped based on your income. Those caps no longer exist. Under Section 71305 of Public Law 119-21, consumers must repay the entire excess amount with no limit.13Centers for Medicare & Medicaid Services. Are There Limits to How Much Excess Advance Payments of the Premium Tax Credit (APTC) Consumers Must Pay Back
You reconcile advance payments on IRS Form 8962 when you file. If the payments made on your behalf exceeded what you actually qualify for based on your real income, you owe the difference in full. Letting the marketplace guess your income from outdated records is the kind of mistake that used to sting and now can be ruinous.
Appeals Are a Separate Process
If you submitted documentation and the marketplace adjusted your eligibility in a way you disagree with, you can file an appeal. The deadline is 90 days from the date of the notice containing the determination you’re challenging.14HealthCare.gov. What Can I Appeal If you miss that window, you can still file and explain why you were late; the appeals entity has discretion to grant extensions for good cause.
Resolving a DMI and filing an appeal are two different things. Resolving a DMI means sending the documents the marketplace requested. An appeal means asking someone to review a decision you believe is wrong. The two can run at the same time, but don’t treat an appeal as a substitute for submitting your documents within the resolution window. Get the documentation in first, and appeal the outcome only if it’s still wrong after the marketplace has reviewed what you sent.