Quick post because I keep seeing the same April tax surprise threads, and most of them trace back to one decision people made in five minutes back in January — their 401(k) election.
Working through this for my own retirement transition, the framework that finally clicked is below. Nothing here is novel, but the 2026 rule changes are catching even informed savers off guard.
The 2026 limits, since they changed:
- $24,500 employee elective deferral
- $32,500 if you're 50+ ($8,000 catch-up)
- $35,750 if you're 60–63 ($11,250 "super catch-up")
- $72,000 combined annual additions cap (includes employer match and any after-tax)
Why elections drive April surprises
The election form looks like an HR formality. It isn't. You're making a tax decision and a withholding decision in the same form, and the two don't automatically reconcile.
Four things worth thinking through:
1. Traditional vs. Roth. Same contribution cap, opposite tax treatment. Traditional lowers 2026 taxable income; Roth doesn't. The clean way to decide: estimate your marginal bracket this year and your expected marginal bracket in retirement. If today's bracket is meaningfully higher, Traditional wins. If lower or roughly equal, Roth wins (and gives you tax diversification later). Splitting is fine if you're genuinely uncertain — just don't let the split substitute for thinking about it.
2. The new high-earner Roth catch-up rule. This is the one I'd flag hardest. Starting in 2026, if you earned more than $150K in FICA wages in 2025, your age-50+ catch-up contributions MUST be Roth. You can't take the deduction. Plenty of people elected Traditional catch-up assuming the deduction would offset their bracket — it won't. Worse, some plans haven't implemented Roth yet, in which case you can't make catch-up contributions at all until they do.
3. Match capture and front-loading. Most plans match per paycheck. If you front-load and hit $24,500 in October, you stop receiving match for November and December — unless your plan does a year-end true-up. Read your SPD. No true-up? Calculate the per-paycheck contribution that hits the cap on your final paycheck of the year. Otherwise it's free money you're walking away from.
4. The W-4 disconnect. This is what actually causes the April surprise. Your withholding was set assuming a certain mix of Traditional vs. Roth contributions and a certain bonus structure. If any of that changed mid-year — RSU vests, spouse income changes, you flipped your contribution mix — your withholding is wrong. Run a quick projection in June and again in October. The IRS Tax Withholding Estimator works for most W-2 situations.
The 401(k) election is probably the highest-leverage tax decision a W-2 employee makes all year. Five minutes of HR-form thinking can cost five figures in April.
Anyone hitting the new Roth catch-up wall this year? Curious how plans are handling implementation — I've heard mixed reports on whether mid-2026 amendments are common.