A sign-on bonus is cash paid for showing up. Employers use it to replace equity or a bonus you are leaving behind, to sweeten an offer without raising the base salary that future raises are built on, or simply to win a competitive hire. It typically arrives in the first month, sometimes split between the first paycheck and the one-year mark.
Two features matter for planning. First, it is taxed as supplemental wages, so 22% federal withholding (2026) comes out, plus Social Security, Medicare, and state tax. A $30,000 sign-on may land as roughly $19,000 to $21,000 in your account. Second, most sign-on bonuses come with a clawback: leave within 12 months (sometimes 24) and you repay some or all of it, often the gross amount rather than what you received.
Because it is one-time, a sign-on does not belong in a monthly budget. It is a lump sum with a date, and the most useful thing to do is decide in advance what it funds: an emergency fund, a moving-cost gap, a debt, or a goal that would otherwise be short.
The common mistake is spending it before the clawback period ends, then being stuck in a job because leaving would mean writing a check. Keeping the repayable portion accessible until the clawback expires keeps your options open.