Pass-through by default: agency profit lands on your 1040
A marketing agency's tax treatment is set by its legal structure, and the default for nearly every independent agency is pass-through taxation. A solo owner with no entity, or a single-member LLC, reports agency revenue and expenses on Schedule C; the net profit is taxed at the owner's personal income tax rates plus 15.3% self-employment tax. An agency with two or more owners, or a multi-member LLC, files a partnership return on Form 1065, and each owner receives a Schedule K-1 showing their share of profit to report personally, generally also subject to self-employment tax for active owners.
The key mental shift for new agency owners: the agency itself pays no federal income tax in these structures. All profit is taxed to you, in the year it is earned, whether you transferred it to your personal account or left it sitting in the agency's bank balance for a slow month. Retained cash is not untaxed cash.
The S corp election and the 21% C corp rate
Two elections change the picture. The common one is the S corporation election, made by filing Form 2553. The agency (still an LLC or corporation legally) then files Form 1120-S, pays the owner a reasonable W-2 salary, and passes remaining profit through on a K-1. The draw: those pass-through distributions avoid the 15.3% self-employment tax, which is why the S corp is the standard structure for agencies with healthy, consistent profit.
The rarer route is C corporation taxation, where the company pays a flat 21% federal tax on its own profit. The catch is double taxation: money paid out to owners as dividends is taxed again on their personal returns. For a service business whose owners want to live on the profits, that usually loses to pass-through treatment, so C corp status mostly appears at agencies retaining large profits for acquisitions or raising outside investment.
Taxed on profit, not on revenue
Whatever the structure, tax applies to net profit: retainers and project revenue minus contractor payments, payroll, software, ad spend billed through the agency, office costs, and every other ordinary business expense. A $600,000-revenue agency paying $350,000 to contractors and $100,000 in tools and overhead is taxed on $150,000, which is why clean books are the difference between a fair bill and an inflated one.
Two operating consequences follow. First, nobody withholds tax on client retainers, so owners of pass-through agencies pay quarterly estimated taxes (April 15, June 15, September 15, January 15) or run salary withholding through an S corp. Second, state taxes stack on top: most states mirror the federal pass-through treatment, several add entity-level fees or franchise taxes, and owners pay state income tax where they live. The structure question, sole prop, partnership, S corp, or C corp, is worth revisiting whenever profit steps up a tier, because the right answer changes as the agency grows.