End-of-Year MAGI Levers When Income Exceeds the 400% FPL Cliff

The 400% FPL cliff in 2026 creates a cliff-shaped discontinuity in tax liability: $1 of additional MAGI at exactly the 400% FPL threshold can trigger a zero-to-full clawback of APTC. A married household that received $14,000 in APTC during 2026 and ends the year at 401% FPL ($84,960 × 1.0025 = $85,172 for HH=2) owes the full $14,000 back. The same household at $84,959 MAGI owes zero — and keeps the $14,000. This is not a marginal-rate phenomenon; it is a cliff.

The ACA's design allows for a critical planning window: MAGI-reducing adjustments can be made AFTER the tax year ends but BEFORE the return is filed. This post-year, pre-filing window is the last opportunity to pull MAGI below the cliff and convert an unlimited clawback into zero liability. The specific levers available, each with its own deadline and dollar limit:

Traditional IRA contributions for the prior tax year may be made up to April 15 of the following year (October 15 if extended — but only if you establish the account by April 15 for SEPs). The 2026 IRA contribution limit is $7,000 ($8,000 if age 50 or older). Deductibility phases out based on AGI and whether you or your spouse is covered by a workplace plan: if neither spouse participates in a workplace plan, the full amount is deductible regardless of income. If one spouse has a workplace plan, phaseout begins at $126,000 AGI (MFJ, 2025; verify 2026 limits). For self-employed individuals with no workplace plan, this is often a clean deduction.

HSA contributions for a prior year may also be made up to the tax filing deadline (April 15, or extended to October 15 for individuals who extend). The 2026 HSA limits: $4,300 self-only, $8,550 family (verify; HSA limits published by IRS in May annually). You must have been enrolled in an HSA-qualified HDHP during the months to which the contribution applies — HSA contributions are tied to months of HDHP coverage. If you were on a non-HSA-eligible plan (e.g., most PPOs), you cannot make HSA contributions for those months.

SEP-IRA contributions for self-employed individuals can be made up to the extended return deadline — October 15 if a timely extension is filed. This is the most powerful lever for high-income self-employed filers: up to 25% of net self-employment income (after the ½ SE tax deduction), with a dollar limit of $70,000 for 2025 (verify 2026 limit). A self-employed person whose net SE income is $100,000 can contribute $23,000+ to a SEP-IRA as late as October 15, 2027 (for TY2026 returns on extension), and the contribution reduces the TY2026 MAGI filed on that return. Solo-401(k) employee deferrals must be made by December 31 of the tax year — they cannot be made after the year ends. The employer profit-sharing portion of a Solo-401(k) can be contributed up to the extended return deadline, paralleling the SEP-IRA.

Qualified Charitable Distributions are different: they must be made during the tax year (before December 31). A QCD made in January 2027 applies to TY2027, not TY2026. This makes QCDs a within-year tool, not a post-year tool. For taxpayers approaching year-end above the cliff, a December QCD can reduce MAGI if they are age 70½ and have a traditional IRA. Planning QCDs proactively in December, rather than reactively in January, is the correct sequence.

The order of operations for maximum cliff-avoidance leverage: (1) Estimate year-end MAGI in November-December. (2) If above the cliff, calculate the MAGI gap (cliff amount minus projected MAGI). (3) Fill the gap with the highest-deadline lever first: QCDs (must be December), then traditional IRA (April 15), then HSA (April 15), then SEP-IRA (October 15). (4) Each dollar contributed reduces MAGI one-for-one, restoring PTC.

The post-year contribution window is one of the most powerful and underused features of the US tax system for ACA purposes. A taxpayer who discovers in March 2027 that their 2026 MAGI is $3,000 above the 400% FPL cliff — and that they owe $14,000 in APTC — has until April 15, 2027 to make a $3,000 traditional IRA contribution that reduces 2026 MAGI by $3,000, dropping it below the cliff, eliminating the $14,000 clawback entirely. The $3,000 IRA contribution saves $11,000 in net liability (after the IRA contribution itself). Few financial moves have a better immediate return.

The key constraint is eligibility. The traditional IRA deductibility phaseout affects high earners with workplace plans. For a MFJ household at 400% FPL (~$84,960 for HH=2 in 2026), both spouses' incomes might well clear the $126,000 MFJ phase-out ceiling — making the IRA deductible. But if one spouse contributes to a 401(k), the non-participant spouse phase-out ceiling is higher ($236,000 for 2025; verify 2026), making the spousal IRA fully deductible up to $200,000 AGI. This distinction — participant spouse vs. non-participant spouse IRA phaseouts — is critical and often missed.

Self-employed individuals with access to SEP-IRA or Solo-401(k) have the most powerful post-year lever. A self-employed person with $110,000 Schedule C net income (after ½ SE tax) can contribute 25% = $27,500 to a SEP-IRA. If their MAGI before the contribution was $97,000 for HH=2 (above the $84,960 cliff), and the cliff gap is $12,040, contributing $12,040 to a SEP-IRA is sufficient to restore full PTC and eliminate the clawback. The October 15 extended deadline gives ample time to calculate the exact contribution needed after examining all other income and deductions.

Capital gains realized near year-end present the steepest cliff risk because they are often not fully known until December and cannot be un-done after the sale. A taxpayer who harvested $10,000 of long-term gains in November and discovers in December that this pushed MAGI above the cliff has limited options: a December QCD (if eligible), or accepting the clawback and using post-year IRA/SEP contributions to minimize it. The acacliff.com engine's real-time capital-gains slider makes this trade-off visible before the sale is executed.