401(k)

A 401(k) is a Retirement Account your employer sets up for you. Money goes in directly from your paycheck before you ever see it - which eliminates the willpower problem of saving manually.

Two flavors exist, and the choice between them is the Roth vs Traditional decision:

• •Traditional 401(k): Contributions are pre-tax. Your $130,000 salary looks like $110,500 to the IRS if you contribute $19,500. You pay taxes on withdrawal in retirement, at whatever your tax brackets are then.
• •Roth 401(k): Contributions are post-tax. You pay taxes now at today's rate, but withdrawals in retirement are completely tax-free.

The critical feature is the Employer 401(k) Match: your employer deposits additional money into your account based on how much you contribute. A common formula is "100% match on the first 6% of salary" - meaning if you put in 6%, they put in 6%. That's a 100% Guaranteed Return on day one, before any investment returns even enter the picture.

Your employer also selects the menu of investment options available inside the account - typically a set of index funds spanning different Asset Classes. You pick from that menu and make a Capital Allocation decision within a constrained set.

Three reasons this matters beyond your own paycheck:

1. Total Compensation math. When you evaluate a job offer - or design compensation for your team - salary is only part of the picture. A $130,000 salary with a 6% Employer 401(k) Match is actually $137,800 in Total Compensation from the 401(k) alone, before you count insurance, HSA, or Equity Compensation. Operators who ignore this misprice Labor.

2. The highest-ROI dollar you'll ever allocate. The match is a Guaranteed Return of 50-100% depending on the formula. No investment - not index funds, not real estate, not Equity Compensation - offers that risk-adjusted profile. Your marginal dollar allocation should always fill the match before flowing anywhere else.

3. Cost Structure awareness. When you're running a P&L, 401(k) matching is part of your Labor cost. If your team has 20 engineers at $150,000 average salary with a 4% match, that's $120,000/year in matching costs sitting in your Cost Structure. It's real money on your Operating Statement. Understanding this helps you reason about the true unit cost of each hire and why benefits aren't "free" from the company's perspective.

Contribution mechanics:

You choose a percentage of each paycheck to route into your 401(k). The federal government sets an annual [UNDEFINED: contribution limit] - for 2024, it's $23,000 if you're under 50. Your employer's match does NOT count toward your limit, so with a 6% match on a $130,000 salary, you could put in up to $23,000 of your own money plus $7,800 from the employer = $30,800 total flowing into the account each year.

Matching formulas:

Common patterns you'll see:

• •Dollar-for-dollar up to X%: Employer matches 100% of your contribution up to 6% of salary. You contribute 6%, they contribute 6%.
• •50 cents on the dollar up to X%: Employer matches 50% of your contribution up to 6%. You contribute 6%, they contribute 3%.
• •Tiered: 100% on first 3%, then 50% on next 2%. You contribute 5%, they contribute 4%.

The decision rule is simple: always contribute at least enough to capture the full match. Contributing less is literally declining free compensation.

[UNDEFINED: Vesting] schedules:

Here's the catch - the employer's match money may not be fully yours immediately. Many companies use a [UNDEFINED: vesting] schedule where you earn ownership gradually over 3-6 years. If you leave after 2 years on a 4-year schedule, you might only keep 50% of the match. Your own contributions are always 100% yours. This matters when you're evaluating whether to stay or leave - unvested match money is a real switching cost.

Investment selection:

Once money is in the account, you choose from the plan's menu - usually index funds, [UNDEFINED: target-date funds], and sometimes company stock. Most plans have a sensible default option. If you don't want to optimize further, the default is usually acceptable. If you do, this is a Portfolio Construction exercise within a constrained set of Investment Instruments.

Liquidity constraint:

Money in a 401(k) is generally locked until age 59.5. Early withdrawals trigger Tax Penalties - typically a 10% penalty on top of income taxes at your current tax brackets. This is a real Liquidity tradeoff: you get tax advantages and Compounding, but you sacrifice access. For someone with a long Time Horizon, the tradeoff is almost always worth it. But it means your 401(k) is an illiquid asset - do not count it as part of your Emergency Fund.

The priority stack for your marginal dollar allocation:

1. 1)Contribute up to the Employer 401(k) Match. This is the Guaranteed Return. Do this before anything else except servicing high-interest debt above ~20% APR.
2. 2)Build your Emergency Fund if it doesn't exist yet. You need Liquidity before you lock more money away.
3. 3)Pay off high-interest debt - if you're carrying a balance at 24% Penalty APR, the return on paying it down beats any investment.
4. 4)Max out HSA if your employer offers one - it's the only account with tax advantages on the way in, while invested, and on the way out.
5. 5)Max out 401(k) to the [UNDEFINED: contribution limit] - now you're getting the tax advantage without the match, which is still valuable depending on your tax brackets.
6. 6)Invest in taxable accounts - only after all tax-advantaged space is full.

Roth vs Traditional decision criteria:

• •If your current tax brackets are higher than you expect in retirement: Traditional. Deduct now at the high rate, pay later at the lower rate.
• •If your current tax brackets are lower than you expect at peak career or in retirement: Roth. Lock in today's low rate, withdraw tax-free later.
• •Early-career operators earning below their expected peak income should usually lean Roth.
• •Genuinely uncertain? Split contributions 50/50 between Traditional and Roth. Diversifying across tax treatment is a valid Allocation strategy when your future tax brackets are hard to predict.

The 401(k) builds directly on two concepts you've already learned. From Retirement Accounts, you know this account is an Asset on your personal Balance Sheet recorded at market value - your net worth moves with the market even when your savings behavior is steady. From pre-tax vs post-tax, you understand why the Traditional vs Roth choice matters: a pre-tax dollar contributed today is worth more than a post-tax dollar, but you'll owe taxes on Traditional withdrawals later at whatever your tax brackets are then. The 401(k) is where these two ideas become operational - it's the specific vehicle where you make the pre-tax vs post-tax decision with real money every pay period. This node connects forward to Employer 401(k) Match for deeper mechanics of matching formulas and how to evaluate them across job offers, Roth vs Traditional for the full tax bracket analysis, Total Compensation for reasoning about the complete value of a compensation package beyond base salary, and HSA as another tax-advantaged account that often appears alongside the 401(k) in benefits enrollment and follows a similar contribute-then-invest pattern.