Sales tax is the question marketing consultants ask last and should ask first, because unlike income tax it is owed to states, it varies wildly by state, and getting it wrong means you owe tax you never collected from clients.
Most states leave pure consulting services alone
Sales tax in the United States grew up around the sale of physical goods, and in the majority of states, professional services, strategy engagements, marketing audits, positioning work, campaign planning, advisory retainers, remain outside the tax base. If your deliverable is thinking, delivered as advice, meetings, and documents, most states have no sales tax for you to charge. That is the general rule, and it is why many consultants operate for years without a sales tax account and are perfectly compliant.
But the general rule is not universal, and the exceptions are not obscure. A handful of states tax services broadly by default: Hawaii through its general excise tax, New Mexico through its gross receipts tax, and South Dakota, among others, sweep most services into the base unless specifically exempted. Several more states tax enumerated service categories that can touch marketing work, things like advertising services, information services, or data processing in certain states. The pattern to internalize: in most states services are exempt unless listed as taxable, but in a few, services are taxable unless listed as exempt.
When deliverables push you over the line
Even in states that spare consulting, what you hand over can change the answer. Tangible deliverables, printed brochures, signage, branded merchandise you procure and resell, are classic taxable sales. Software and SaaS you resell or license, website templates, stock assets, and some digital products are taxable in a growing list of states. Bundling is the trap: a strategy retainer invoiced as one line with taxable deliverables mixed in can, in some states, make the entire invoice taxable. Itemizing consulting separately from taxable goods on your invoices is cheap insurance.
Remote work adds the nexus question. Sales tax generally follows where the customer receives the benefit, and since the Wayfair decision, states can require out-of-state sellers to register once their sales into the state pass economic nexus thresholds. A solo consultant selling untaxed services rarely trips these, but a consultant selling taxable digital products nationally can.
Registering, or confirming you do not need to
The homework is finite: check the rules in your own state and in any state where your clients are concentrated, specifically how they treat consulting or advertising services and any digital goods you sell. State revenue department websites publish taxability guides, and a short consult with a state-savvy accountant settles edge cases. If you do owe collection, you register for a sales tax permit, add the tax to invoices, and file returns on the state's schedule. One reassurance while you sort it out: sales tax is separate from income tax. Charging no sales tax, correctly, does not reduce your federal obligations, and your Schedule C, self-employment tax, and quarterly estimates continue exactly as before.