ACA Hours of Service: Counting Rules, Look-Back Method, and ALE Status

Under the Affordable Care Act, ACA hours of service include every hour an employee is paid to work plus every hour of paid leave, and they decide who counts as full-time at the 30-hour-per-week or 130-hour-per-month threshold. If you employ 50 or more full-time and full-time-equivalent workers, that count also decides whether you must offer coverage at all. Miscounting is where most compliance trouble begins, because the IRS matches what employers report on annual returns against what employees file on their own taxes.

What Counts as an Hour of Service

The regulation at 26 C.F.R. § 54.4980H-1(a)(24) defines an hour of service as each hour for which an employee is paid or entitled to pay. That splits in two. The first category is straightforward: every hour spent performing duties for the employer. The second catches employers off guard: every hour the employee is entitled to payment even when no work is being performed.

Paid leave sweeps in more hours than most employers expect. Vacation, holidays, sick leave, and short-term disability all generate hours of service so long as the employee is being paid. Jury duty and military leave count when the employer pays for that time. A general paid leave of absence qualifies under the same logic. The rule prevents employers from stripping someone’s full-time status because they used standard benefits or exercised protected rights.

What Does Not Count

A few categories are carved out. Volunteer hours for a government entity or tax-exempt organization do not count, provided the work is genuinely voluntary and not a condition of employment. Hours logged through a federal or state work-study program are also excluded.¹ Services performed entirely outside the United States are disregarded, since the employer mandate focuses on the domestic workforce.

The 30-Hour Week and 130-Hour Month Threshold

A full-time employee under the ACA is anyone who averages at least 30 hours of service per week, or at least 130 hours of service in a calendar month.¹ The 130-hour figure is not simply 30 multiplied by 4.33 weeks; the IRS chose it as a workable monthly proxy. Hitting either benchmark in a given month makes the employee full-time for that month.

Reaching the threshold triggers the employer’s obligation to offer minimum essential coverage. An applicable large employer that fails to offer coverage to substantially all full-time employees faces a penalty under Section 4980H(a); one that offers coverage that is unaffordable or provides insufficient value faces a separate penalty under Section 4980H(b).²

Counting Hourly Employees

For workers paid by the hour, the regulations require employers to count actual hours of service, drawn from contemporaneous timekeeping or payroll records.³ Estimates and averages are not acceptable for hourly staff. If you run a time-clock system or digital timekeeping platform, you already have what you need.

Consistency across employee categories is mandatory. You cannot switch counting methods within the same group to push certain individuals below the 130-hour line. Once you pick a method for a classification, it applies uniformly through the relevant measurement or stability period.

Counting Non-Hourly Employees

Salaried professionals, managers, and other non-hourly staff often have no time clock. The regulations give employers two standardized equivalency methods as alternatives to counting actual hours.³

Days-worked equivalency credits the employee with 8 hours for each day they are entitled to pay for at least one hour of service. This works well for staff with predictable daily schedules but varying weekly commitments.
Weeks-worked equivalency credits the employee with 40 hours for each week they are entitled to pay for at least one hour of service. This is the simpler choice for salaried workers who maintain a consistent weekly presence, and it integrates cleanly with weekly or biweekly payroll cycles.

You can also track actual hours for non-hourly employees. That third option makes the most sense when salaried employees have highly irregular schedules and an equivalency would overstate or understate their hours.

Whichever approach you pick, it cannot systematically undercount hours for people who are actually working full time. If a salaried employee regularly works more than 30 hours a week and the equivalency suggests otherwise, the IRS can require you to switch to actual-hour tracking. The equivalencies are a convenience, not a loophole.

Variable-Hour Employees and the Look-Back Method

When someone’s schedule fluctuates enough that you cannot tell at hire whether they will average 30 hours a week, the look-back measurement method offers a structured way to make that determination over time rather than guessing month to month.⁴

Standard Measurement Period for Ongoing Employees

You select a measurement period lasting between 3 and 12 consecutive calendar months and apply it uniformly to all employees in the same category. During that window, you track whether each employee averages at least 30 hours of service per week.⁴

If the employee hits the 30-hour average during the measurement period, you must treat them as full-time for the entire subsequent stability period, no matter what they work during that time. The stability period must be at least 6 months long and at least as long as the measurement period. If the employee falls below 30 hours, you may treat them as non-full-time during a stability period that is no longer than the measurement period.⁴

Initial Measurement Period for New Hires

New variable-hour and seasonal employees get their own initial measurement period, also between 3 and 12 months, beginning around the start date. Same logic: average 30 or more hours and they lock in full-time status for the stability period; fall short and you can treat them as non-full-time. The combined initial measurement period and any administrative period cannot push the coverage effective date past 13 months from the start date, plus any partial month remaining.⁵

Administrative Period

Between the measurement period and the stability period, you may build in an administrative period to process the data, notify employees of their status, and enroll those who qualify. This gap cannot exceed 90 days and cannot create an unreasonable delay in coverage for employees determined to be full-time.

Special Situations

FMLA, USERRA, and Other Protected Leave

Unpaid leave under the Family and Medical Leave Act or the Uniformed Services Employment and Reemployment Rights Act needs careful handling. These absences do not generate hours of service in the usual sense because no pay is involved, but employers using the look-back method must account for them. The standard approach is to exclude FMLA and USERRA periods from the measurement calculation entirely, so the absence does not drag down the employee’s average. Exercising a federally protected right should not cost someone their full-time status.

Rehires and Breaks in Service

When a former employee returns after a gap, you have to decide whether to treat them as a new hire or a continuing one. Under the ACA regulations, the dividing line is a break of at least 13 consecutive weeks with no hours of service. If the gap reaches 13 weeks, you may restart the measurement process from scratch. Educational institutions get a longer threshold of 26 consecutive weeks, reflecting the reality of extended academic breaks. Gaps shorter than 13 weeks mean the returning worker picks up where they left off.

On-Call and Layover Hours

On-call time and layover hours are among the harder judgment calls. The IRS does not have a single bright-line rule; employers must use a reasonable method consistent with the employer mandate regulations. The general principle is that if the employer restricts the employee’s ability to use the time freely, those hours should count.¹

Rolling Hours Up Into ALE Status

Your total workforce for ALE purposes is not just a headcount of full-time employees. Part-time employees factor in through a full-time equivalent calculation. For each calendar month, add up the hours of service for all non-full-time employees (capping any single person at 120 hours) and divide by 120. That quotient is your FTE count for the month.⁶

To determine ALE status for a given year, add your actual full-time employee count to your FTE count for each month of the preceding calendar year, then divide by 12. If that average hits 50 or more, you are an applicable large employer for the current year.²

Seasonal Worker Exception

Employers whose headcount only crosses the 50-employee line because of seasonal labor may avoid ALE status entirely. The exception applies when two conditions are both met: the workforce exceeded 50 full-time employees (including FTEs) for 120 days or fewer during the preceding calendar year, and every employee above 50 during that window was a seasonal worker.² The IRS defines seasonal workers as those performing labor on a seasonal basis under Department of Labor standards, plus retail workers hired exclusively for holiday seasons. Employers may apply a reasonable, good-faith interpretation.⁷

What Miscounting Costs

Inaccurate hour tracking is not just a paperwork problem. For the 2026 calendar year, the IRS has announced the following inflation-adjusted penalty amounts:⁸

Under Section 4980H(a), an ALE that fails to offer minimum essential coverage to at least 95 percent of its full-time employees owes $3,340 per year for each full-time employee, minus the first 30. It applies across the board even if only one employee receives a subsidized marketplace plan.
Under Section 4980H(b), an ALE that offers coverage but the coverage is unaffordable or fails to provide minimum value owes $5,010 per year for each full-time employee who actually receives subsidized marketplace coverage. Per person rather than across the workforce, but it adds up fast in larger organizations.

The IRS flags potential liability through Letter 226-J, which proposes an employer shared responsibility payment based on the forms the employer filed and the tax returns filed by its employees. You have a specific deadline stated in the letter to respond using Form 14764, either agreeing with the assessment or disputing it with supporting documentation. If you disagree, the IRS will issue a determination letter that includes information about your right to appeal.⁹

1
Internal Revenue Service. Identifying Full-Time Employees
2
Office of the Law Revision Counsel. 26 USC 4980H – Shared Responsibility for Employers Regarding Health Coverage
3
eCFR. 26 CFR 54.4980H-3 – Determining Full-Time Employees
4
Internal Revenue Service. Notice 2012-58
5
eCFR. 45 CFR 147.116 – Prohibition on Waiting Periods That Exceed 90 Days
6
Internal Revenue Service. Determining if an Employer Is an Applicable Large Employer
7
Internal Revenue Service. Questions and Answers on Employer Shared Responsibility Provisions Under the Affordable Care Act
8
Internal Revenue Service. Rev. Proc. 2025-26
9
Internal Revenue Service. Understanding Your Letter 226-J