ACA Subsidy Cliff
One extra dollar of income can cost a household thousands of dollars in health insurance subsidies — that’s the cliff.
What Is It
ACA premium subsidies — the premium tax credit — are calculated based on income as a percentage of the federal poverty line (FPL). At exactly 400% of FPL, the subsidy doesn’t taper off gradually — it disappears entirely. Crossing that line by even a small amount, from a bonus, a Roth conversion, or extra freelance income, can mean losing a subsidy worth thousands of dollars a year, all at once, not gradually. The income measured is MAGI — Modified Adjusted Gross Income — which is broader than take-home pay and includes things like realized capital gains and the taxable portion of a Roth conversion.
Why It Matters
This is why healthcare costs are a genuine, load-bearing part of financial planning for early retirees and anyone managing income near that threshold. A single decision that adds to MAGI — a Roth conversion is the most common one FIRE-community readers will run into, since it’s an entirely voluntary income event — can trigger the cliff even if every other part of a plan is sound.
This is exactly why the ACA Subsidy Calculator’s results specifically show “headroom” as one of its outputs — how much additional MAGI is available before hitting 400%, so a decision like a conversion can be sized to stay under the line on purpose, rather than discovered after the fact.
Quick Example
A household sitting at 395% of the federal poverty line qualifies for a meaningful premium subsidy. One additional dollar of MAGI — crossing to 401% — doesn’t shrink that subsidy, it eliminates it completely. The distance between “meaningful help” and “none at all” can be a single dollar of income, not a gradual slope.
Try It Yourself
See exactly where your own household sits relative to the cliff — and how much headroom you actually have.
💊ACA Subsidy Calculator
Model ACA subsidy cliffs and headroom for Roth conversions and capital gains in early retirement.