Report Your Income And Expenses First
As a consultant, you're self-employed, which means the IRS treats your business as separate from your personal tax return but taxed through it. You report gross revenue from all clients, minus business expenses like software, home office costs, travel, and contractor fees, on Schedule C. The result is your net profit, and that number flows to your Form 1040 as taxable income.
Clients who paid you $600 or more during the year should send you a 1099-NEC, and payment processors may send a 1099-K if you were paid through platforms like PayPal or Stripe above the current-year threshold. But even if a client forgets to send a form, you're still required to report every dollar of income.
Calculate And Pay Self-Employment Tax
Because no employer withholds Social Security and Medicare on your behalf, you owe self-employment tax on your net profit, calculated on Schedule SE. This is 15.3% (12.4% Social Security up to the annual wage base, plus 2.9% Medicare) on top of regular income tax. This is the number most consultants underestimate: on a $150,000 net profit year, self-employment tax alone can exceed $15,000, before federal and state income tax are added.
The good news is you get to deduct half of your self-employment tax as an adjustment to income, which softens the blow slightly.
Pay Quarterly, Not Just Once A Year
The IRS expects tax paid throughout the year, not in one lump sum in April. If you expect to owe $1,000 or more, you're required to make estimated payments using Form 1040-ES, due in mid-April, mid-June, mid-September, and mid-January of the following year. Missing these dates triggers an underpayment penalty, calculated as interest on the shortfall, even if you pay everything in full by the annual filing deadline.
This is where consultant cash flow gets tricky. Retainers and project fees rarely arrive evenly. You might land a six-figure engagement in Q2 and go quiet in Q3, but your estimated tax obligation doesn't know that unless you recalculate it each quarter based on actual year-to-date profit rather than dividing last year's tax bill by four.
Set Aside Money As You Get Paid
The most reliable system is to treat every incoming payment as only partially yours. A common approach is to move 25% to 35% of each payment into a separate savings account the moment it lands, adjusting the percentage based on your total income level and state tax rate. High earners in high-tax states may need to set aside closer to 40%.
If you operate through an S corporation election because your consulting income is high enough to justify it, part of your compensation comes as W-2 salary with payroll withholding, and the rest as distributions. That changes the mechanics: payroll taxes get paid through regular payroll runs instead of Schedule SE, but you still typically owe quarterly estimates on the distribution portion.
Know Your Deadlines
Your annual return, Schedule C and Schedule SE included, is due by the standard mid-April deadline, or mid-March if you're filing as an S corporation. Extensions push the paperwork deadline but not the payment deadline. Interest and penalties still accrue on unpaid tax from the original due date, so an extension only buys you time to file, not time to pay.