401(k)
A 401(k) is a US employer-sponsored retirement account that lets you invest part of each paycheck before taxes are taken out. Your money grows tax-deferred, and many employers match a portion of what you contribute — effectively free money. Withdrawals in retirement are taxed as ordinary income.
Example
Contributing 10% of a $70,000 salary with a 50% employer match up to 6% adds $9,100 per year to your retirement savings.