Every year, thousands of employers receive IRS penalty notices tied to Affordable Care Act reporting errors — and most of them were caught off guard. The ACA's employer mandate sounds straightforward on paper, but the reporting mechanics, affordability calculations, and filing deadlines create a compliance minefield that trips up even experienced HR teams. Whether you're approaching the 50-employee threshold for the first time or you've been filing for years and aren't fully confident in your process, this guide walks you through exactly what the law requires and where employers most commonly go wrong.

Who Must Comply: Understanding Applicable Large Employer Status

The ACA's employer shared responsibility provisions apply to Applicable Large Employers (ALEs) — organizations that employed an average of at least 50 full-time or full-time-equivalent employees during the prior calendar year. This threshold sounds clear, but calculating it correctly is where many businesses stumble.

Full-time employees are those working 30 or more hours per week (or 130 hours per month). Part-time hours are aggregated and divided by 120 to produce full-time equivalents. Seasonal worker rules, controlled group rules for related businesses, and mid-year workforce fluctuations all affect the final ALE determination. If your headcount hovers near 50, getting this calculation right is critical — the difference between ALE and non-ALE status determines whether your entire ACA compliance obligation exists at all.

Non-ALEs are not subject to the employer mandate or the associated reporting requirements under IRC Sections 6055 and 6056, though they may still have state-level reporting obligations depending on where they operate.

The Employer Shared Responsibility: What Coverage You Must Offer

Once you're classified as an ALE, you must offer minimum essential coverage (MEC) to at least 95% of your full-time employees and their dependents. That coverage must also meet two additional tests:

  • Minimum value: The plan must pay at least 60% of the total cost of benefits under the plan.
  • Affordability: The employee's required contribution for self-only coverage cannot exceed a set percentage of their household income. For 2024, the IRS affordability threshold is 8.39% of household income. Because employers rarely know an employee's actual household income, the IRS provides three safe harbor methods — the W-2 wages safe harbor, the rate of pay safe harbor, and the federal poverty line safe harbor — to establish affordability without that data.

Failing to offer coverage to 95% of full-time employees triggers the 4980H(a) penalty — sometimes called the "sledgehammer" penalty — assessed across nearly your entire full-time workforce. Offering coverage that isn't affordable or doesn't meet minimum value triggers the narrower 4980H(b) penalty, applied only for employees who obtain subsidized marketplace coverage. Both can result in significant annual liability.

ACA Employer Reporting: Forms 1094-C and 1095-C

ALEs must report health coverage information to the IRS and furnish statements to employees each year. This is done through two forms:

  • Form 1095-C — Provided to each full-time employee, this form documents the coverage offered, the lowest-cost premium available, and the employee's enrollment status month by month throughout the year.
  • Form 1094-C — The transmittal form filed with the IRS along with all 1095-C forms, summarizing the employer's workforce and coverage data at the entity level.

Key deadlines to calendar every year:

  1. January 31: Deadline to furnish Form 1095-C to employees (the IRS has historically granted short extensions, but you should not plan around them).
  2. February 28 / March 31: Paper and electronic filing deadlines, respectively, for submitting Forms 1094-C and 1095-C to the IRS. ALEs filing 10 or more information returns must file electronically.

Errors on these forms — incorrect employee names or Social Security Numbers, wrong plan codes, missing months of coverage — can trigger IRS notices and penalties of up to $330 per incorrect return, with no cap for intentional disregard.

Common ACA Compliance Mistakes That Invite Penalties

The IRS continues to actively audit ACA filings. The most frequent errors employers make include:

  • Miscalculating ALE status due to improper FTE aggregation or ignoring controlled group rules
  • Using incorrect Line 14 and Line 16 indicator codes on Form 1095-C
  • Failing to apply affordability safe harbors correctly, leaving the employer exposed to 4980H(b) penalties
  • Missing the furnishing deadline for employee copies
  • Not tracking coverage offers and waivers month by month during the year, making year-end reporting a scramble

Penalty assessments often arrive as IRS Letter 226-J, sometimes years after the filing in question. By then, reconstructing monthly coverage data is far more difficult and expensive than getting it right from the start.

How Outsourcing ACA Administration Reduces Your Risk

ACA compliance requires accurate, month-by-month data from payroll, benefits enrollment, and HR systems working in sync. For many employers — especially those growing quickly or managing a distributed workforce — keeping those data streams aligned internally is where errors creep in.

An experienced Administrative Services Organization like Nomad Partners manages the full ACA compliance cycle: ALE status determination, affordability analysis, month-by-month coverage tracking, and timely preparation and filing of Forms 1094-C and 1095-C. Because we integrate payroll administration and benefits administration under one roof, the data required for accurate reporting is already organized and auditable — not assembled in a panic each January.

ACA penalties are almost entirely avoidable with the right process. The cost of getting it wrong consistently outweighs the cost of doing it right.

If you're uncertain about your ALE status, your affordability calculations, or whether your current reporting process is airtight, reach out to the Nomad Partners team. We'll review your situation and help you build a compliance process that holds up under IRS scrutiny — so you can focus on running your business.