On paper a consulting practice is the easiest business to keep books for. No inventory, no crew, a short vendor list. In practice, consultants' books are often a mess, because income arrives in lumps, business and personal spending share a laptop and a phone, and each billing arrangement, whether retainer, milestone, hourly, or a flat project fee, raises its own accounting question.
This guide covers the handful of things that separate clean consulting books from messy ones, so you know your real margin, your accountant has what they need, and a client's advance payment never gets mistaken for profit.
Retainers, milestones, and when income is really income
Most consultants keep books on the cash basis: income is recorded when the money arrives and expenses when they are paid. That is simple and it is what the tax return will use. The trap is the retainer. A client who pays three months in advance has handed you cash that is taxable when received on the cash basis, but it is not yet earned. If the books show it as plain revenue and you spend it, you have a quarter of work ahead with no money to fund it. Track unearned retainers separately, either as a liability account that you draw down as the work is delivered or at minimum in a memo schedule you review monthly. A non-refundable engagement fee is different: it is earned when the client commits and can be recorded as revenue outright.
Milestone billing creates the opposite problem. You may have done six weeks of work that has not yet reached an invoiceable milestone, so the books understate what you have earned. Keep a simple work-in-progress list of earned-but-unbilled work so you are not misled by a quiet month in the bank account. Hourly engagements need time tracking that feeds the invoice directly, so every hour is billed and nothing is reconstructed from memory at month end. If the practice grows, or you want financials that show income when it is earned rather than when it is collected, talk to your accountant about the accrual basis. For most solo consultants, cash basis with a disciplined retainer schedule is enough.
Billable expenses and client reimbursements
Travel, software licenses, and subcontractors that you pass through to a client are the most common source of distorted consulting margins. There are two correct ways to handle them. The gross method records the cost as an expense when you pay it and the client's reimbursement as income, typically in a reimbursed-expenses income account. The pass-through method books the cost directly to a receivable or clearing account so it never touches the Profit and Loss. Either works. What does not work is mixing them, or netting a reimbursement against an unrelated expense line, which quietly misstates both revenue and costs.
The gross method has a practical advantage: when a client issues you a Form 1099-NEC, it usually includes the reimbursements they paid you, so gross books reconcile to what the client reported. Any markup you add to a pass-through cost is plain income. If you hire subcontractors, collect a Form W-9 before the first payment and track what you pay each one; for payments made in 2026 the 1099-NEC reporting threshold is generally $2,000, so confirm with your accountant who needs a form in January. Keep the receipt behind every billable expense. The client may ask for it, and so may the IRS.
The deductions consultants miss, and the ones they overclaim
Commonly missed: a home office used regularly and exclusively for the practice, the business share of phone and internet, professional liability insurance, memberships and certifications, courses that maintain or improve the skills you already sell, and the software stack you forget about because it bills annually. Travel to client sites is deductible, including airfare, lodging, and half of meals while away, with one caution. If an engagement puts you at a single client location for long enough that it becomes your regular place of work, the daily trip there can turn into nondeductible commuting; the general rule is that a work location expected to last a year or less is temporary. Keep a mileage log for local client visits, and record business use of a personal car as mileage rather than running the car payment through the business.
Commonly overclaimed: ordinary clothing, the entire personal phone bill, meals with no documented business purpose, and social events labeled as networking. Two items trip up owners of sole proprietorships in particular. Self-employed health insurance is deducted on your personal return, not as a business expense, so if the premium is paid from the business account, code it to owner's draw. And courses that qualify you for a new line of work, rather than improving your current one, are not deductible at all.
Entity choice and paying yourself
As a sole proprietor or single-member LLC, every dollar of net profit is subject to self-employment tax, and you pay yourself by taking draws, which are equity transactions and never an expense. Move a fixed percentage of each client payment into a separate tax savings account and make quarterly estimated payments from it. Because consulting income is lumpy, either compute each quarter's payment from what you actually earned or use the safe harbor of paying in what last year's return showed, so a strong fourth quarter does not become an underpayment penalty. Once net profit is consistently well above what a reasonable salary for your work would be, ask your accountant whether an S corporation election makes sense. It can reduce self-employment tax, but it adds payroll, a separate business return, and a requirement to pay yourself a reasonable wage before taking distributions, and the books then have to separate wages, payroll taxes, and distributions cleanly.
Whichever structure you choose, the practice runs better on a monthly close: accounts reconciled, retainers and reimbursements recorded consistently, and a P&L you can price your next engagement from. That is what Evolv Bookkeeping does for $199 per month flat, with your P&L and Balance Sheet delivered by day 2 of the following month and 1099 prep for your subcontractors at year end. If the books are behind, catch-up is $199 for each month behind, done within 2 days and guaranteed in writing. No contracts, cancel anytime, and an instant quote is on our homepage.