01
What is a 401(k)?
A 401(k) is a retirement savings account your US employer sets up. You pick a percentage of each paycheck to contribute, and that money goes in before income tax, which lowers what you owe this year.
Start on day one for one reason: the employer match. Most companies match part of what you put in, often 50% or 100% up to about 3–6% of your salary. That match is extra pay you only get if you contribute, so skipping it leaves money on the table. The 2025 contribution limit is $23,500.
The account is yours when you leave, though employer-match dollars may need a year or two to fully “vest.” Your own contributions always belong to you, and you can roll the whole thing into a new employer’s plan or an IRA when you change jobs.
02
What is an HSA?
A Health Savings Account is the most tax-advantaged account in the US, and most new arrivals have never heard of it. Money goes in before tax, grows tax-free while invested, and comes out tax-free for medical costs. No other US account gives you all three.
To open one you need a high-deductible health plan (HDHP), which is usually one of the options at benefits enrollment. The 2025 limit is $4,300 for an individual.
Unlike an FSA, an HSA is not use-it-or-lose-it: unused money rolls over and stays yours every year. After 65 you can withdraw it for anything, like a regular retirement account. Plenty of people treat a maxed HSA as a stealth retirement fund.
03
How are RSUs taxed?
Restricted Stock Units are taxed twice, and the first time catches almost everyone.
When your RSUs vest, the IRS counts their full value that day as ordinary income, the same as salary, whether or not you sell. Your company withholds tax automatically, but usually only at the 22% supplemental rate. If your total comp lands you in a higher bracket, often 32–35% or more, you owe the difference when you file in April. That gap is the surprise bill.
The fix: file a new W-4 in your first weeks asking for extra withholding so the shortfall doesn’t pile up. When you later sell the shares, that’s a separate event, and you owe capital-gains tax only on any increase since the vest date. Selling right at vest usually means little or no extra gain.
04
How US credit scores work
A three-digit credit score (FICO, 300 to 850) decides whether you can rent, get a card, or finance a car, and what rate you pay. You arrive with no US history, so you score as a blank, not as good or bad.
You build a score by borrowing small and repaying on time. The fastest honest start is a secured card: put down a deposit, use it for small purchases, and pay it off in full every month. Make sure it reports to all three bureaus (Experian, Equifax, TransUnion).
Two habits move the score most: paying every bill on time, and keeping your balance well under the limit (under 30%, ideally under 10%). Most people who do this clear 700+ within a year, enough to rent and qualify for normal cards and loans.