2027 open enrollment planning: the enrollment mix risk
Employer health budgets for 2027 assume last year's waiver rate holds. As marketplace, retiree and dependent coverage gets pricier, spouses and waivers return to the plan and per-employee math breaks.
Most 2027 benefit budgets were built the same way they are built every year: take last year's enrollment file, hold the waiver rate and tier mix constant, apply a trend factor, and call it a plan. That is the quiet flaw in 2027 open enrollment planning. Coverage is getting more expensive everywhere at once, and when outside options get worse, people come back to the employer plan.
Why the cost story broke in every channel at once
The consumer-facing version of this story landed in the past two weeks. NBC News reported that people covered through work, through ACA marketplaces and through Medicare are all facing higher 2027 bills. CBS News reported roughly a week earlier that employer and worker health plan costs are expected to jump in 2027. Broker previews of 2027 open enrollment trends and early ACA rate signals are circulating now, which is exactly when January 1 plan-year rates and contribution strategies get locked.
The employer-side numbers have been pointing the same direction for a while. Mercer projected a 6.5% health benefit cost increase for 2026 and described it as the highest in 15 years, with later reporting putting employers on pace for 6.7%. Mercer's mid-2026 update said employers are shifting healthcare costs to employees while also using new approaches to limit the impact. Cost shifting is already the default lever, not the contingency plan.
What is different this cycle is simultaneity. In a normal year, one channel gets expensive and the others absorb the spillover. When employer, marketplace and Medicare pricing all move up together, the household has fewer places to put coverage, and the employer plan is often the least-bad remaining option.
A spouse who joins your plan because their marketplace premium doubled does not show up in any trend forecast. They show up in the January invoice.
Enrollment mix is a volume problem, not a claims problem
Per-employee-per-month is a useful budgeting unit until the denominator changes shape. A spouse who was covered through their own employer or through a marketplace plan last year and enrolls in yours this year does not show up in a trend forecast. Neither does an adult child added back to a family tier, or an employee who took the waiver credit in 2026 and decides the credit is no longer worth the exposure in 2027.
Each of those decisions moves an employee from a cheaper tier to a more expensive one, or from no coverage to coverage. The plan's cost per covered life can hold steady while total plan spend rises, which is the version of a budget miss that is hardest to explain to finance after the fact. SHRM's Total Rewards coverage flagged economic uncertainty as a force shaping how employees behave during open enrollment, and that behavioral shift is the half of the problem most forecasting models do not capture.
The 10.22% affordability ceiling is not a target
The IRS set the 2027 ACA affordability percentage at 10.22%, a change covered in late July 2026 across benefits advisory outlets. Mechanically, it raises the maximum employee-only contribution an applicable large employer can charge while still meeting affordability. That gives employers more legal headroom in the exact cycle when cost pressure is peaking.
The temptation is obvious and the trap is too. Pricing employee-only contributions toward the ceiling protects the budget on paper while pushing lower-paid hourly workers closer to the point where coverage stops being practical. Employers that use the rate of pay or federal poverty line safe harbors instead of W-2, or that tier contributions by pay band, keep compliance intact without loading the increase onto the population least able to absorb it. The safe harbor choice should be a deliberate decision documented before rates lock, not a default inherited from last year's filing.
Three decisions to make before rates lock
First, build an enrollment-mix forecast that stress-tests the waiver rate rather than assuming it. Model what happens if waivers drop by two, five and ten percentage points, and what happens if a share of employee-only enrollees move to employee-plus-spouse or family. The output should be a range of total plan spend, not a single per-employee number.
Second, make an explicit call on spousal surcharge and dependent tier pricing. If a spouse has access to other employer coverage, a surcharge is a legitimate lever, but it needs to be set now and communicated clearly, not bolted on in November. Dependent tier pricing deserves the same scrutiny, because family tiers are where the volume shift concentrates.
Third, plan communication for the employees who waived last year and will not this year. That group has no recent experience with your plan, your network or your deductible structure. They are the most likely to make a poor election and the most likely to be surprised by their first paycheck deduction in January. Treat them as a distinct audience with their own messaging, not as part of the general open enrollment blast.
