A sale from one business to another carries sales tax in every state that has a sales tax, unless the buyer qualifies for a specific exemption and the seller collects the paperwork to prove it. That is the whole framework for business-to-business sales tax. Forty-five states impose sales tax, and each of them starts from the presumption that a sale of tangible personal property is taxable regardless of whether the buyer is a consumer or a company. The question worth asking on any B2B invoice is not whether tax could apply, but whether an exemption fits and whether the documentation is in order.
Why B2B Sales Are Taxable by Default
Sales tax is a consumption tax. The state wants it collected from whoever uses or consumes the product. A business that buys office furniture, cleaning supplies, or computers for its own operations is the end user of those items, and the transaction is taxable in the same way a retail purchase would be. Both sides being commercial does not change that.
The proof burden sits entirely on the seller. If a seller fails to collect tax and cannot produce documentation showing the buyer qualified for an exemption, the seller pays the uncollected tax out of its own pocket. Auditors work from the presumption that every sale is taxable, and they specifically look for purchases that a business treated as exempt without justification. The most common mistake they find is inventory bought under a resale certificate that the buyer ended up consuming internally.
Where a Seller Has to Collect
Before 2018, a seller generally had to collect sales tax only in states where it had a physical presence such as a warehouse, an office, or employees on the ground. The Supreme Court ended that rule in South Dakota v. Wayfair, Inc., holding that “physical presence is not necessary to create a substantial nexus” with a state.1Supreme Court of the United States. South Dakota v. Wayfair, Inc., 585 U.S. (2018) States can now require collection from any seller with enough economic activity in their borders, wherever the seller sits.
Every sales-tax state has since adopted an economic nexus standard. The most common threshold is $100,000 in annual sales into the state, now the rule in over 40 jurisdictions. Some states also trigger collection at 200 separate transactions, though several have dropped the transaction count and rely on the dollar threshold alone. Once a seller crosses either line, it must register, collect, and remit in that state, including on sales to other businesses where no exemption applies.1Supreme Court of the United States. South Dakota v. Wayfair, Inc., 585 U.S. (2018)
This matters for B2B sellers with a national footprint. A manufacturer in one state that ships components to factories in a dozen others could have nexus in all of them based on sales volume alone. Each state has to be evaluated on its own, and the collection obligation does not wait for the seller to notice. It attaches the moment the threshold is crossed.
Exemptions That Actually Apply to B2B Sales
A handful of exemption categories let B2B transactions proceed without tax at the point of sale. Each has its own requirements. Qualifying under one category does not automatically qualify a purchase under another.
Resale
The resale exemption is the most common reason a B2B sale goes untaxed. When a wholesaler sells inventory to a retailer who plans to resell those goods, the wholesaler does not collect sales tax. The tax gets collected later, when the end customer buys the product. Taxing every stage of the supply chain would stack taxes on the same item.
The exemption only works when the buyer genuinely intends to resell the property in the ordinary course of business. If a retailer buys 500 units, sells 480, and keeps 20 for use around the office, those 20 units become taxable and the buyer owes use tax on them. This is where auditors spend a lot of their time, hunting for inventory diverted to internal use without tax paid.
Manufacturing
Most states exempt machinery, equipment, and raw materials used directly in manufacturing a finished product. A factory buying steel that gets stamped into auto parts, or chemicals that become part of a cleaning solution, generally qualifies. The exemption covers items physically transformed or consumed in production.
The tricky word is “directly.” Equipment on the factory floor that shapes, cuts, or assembles a product usually qualifies. Equipment used for administration, storage after production, or quality testing often does not. Many jurisdictions require that the equipment be used predominantly or exclusively in production, so a manufacturer should check its state’s definition before assuming a purchase qualifies.
Government and Nonprofit Purchases
Federal agencies are constitutionally immune from state sales taxes under the intergovernmental tax immunity doctrine.2Constitution Annotated. ArtI.S8.C1.1.5 Intergovernmental Tax Immunity Doctrine The Supremacy Clause prevents states from taxing the federal government.3GSA SmartPay. State Tax Legal History Sellers doing business with federal agencies should not collect tax on those sales, but the transactions still need to be documented.
Nonprofits with 501(c)(3) status often qualify for state sales tax exemptions too, but not automatically. An IRS determination letter alone does not exempt an organization from sales tax. Nonprofits have to apply separately to each state, and the rules vary; some states limit the exemption to certain kinds of organizations or purchases. Sellers should collect a valid state exemption certificate from any nonprofit buyer before leaving tax off the invoice.
Agricultural Use
Businesses engaged in commercial farming can often buy feed, seed, fertilizer, and certain equipment without paying tax. Many states also apply reduced rates or full exemptions to farm machinery and to items consumed directly in crop or livestock production. The specifics vary widely. Some states exempt all farm equipment, others limit the exemption to self-propelled machinery or items used on the farm itself. Sellers dealing with agricultural buyers should collect the right exemption documentation and confirm the buyer holds any required farming permits.
Exemption Certificates: The Document That Protects the Seller
An exemption certificate is what protects a seller when a B2B sale goes untaxed. Without one on file, the seller owns the tax debt if an auditor later questions the transaction. Collecting certificates at the start of every new business relationship is the single most important compliance step in B2B sales.
Every certificate should include the buyer’s legal business name, physical address, and state tax identification or registration number. That registration number is the critical piece: it links the buyer to the state’s tax system and confirms the buyer is authorized to make exempt purchases. The certificate also has to state the reason for the exemption with enough specificity that an auditor reviewing it years later can understand why the sale was untaxed. For resale certificates, the buyer should describe the general category of products it purchases and resells.
Multi-State Forms
Sellers who cross state lines can simplify paperwork by using the Multistate Tax Commission’s Uniform Sales and Use Tax Resale Certificate, a standardized form accepted by multiple jurisdictions.4Multistate Tax Commission. Uniform Sales and Use Tax Resale Certificate – Multijurisdiction The form lets a buyer provide tax information covering several states on one document.
The 24 member states of the Streamlined Sales and Use Tax Agreement also accept a unified exemption certificate. Buyers do not have to be registered through the Streamlined system to use it, but not every exemption listed on the form is valid in every member state. If a buyer is registered in the state where it claims the exemption, it must provide that state’s ID number; if not, it can often supply a sales tax ID from any state.5Streamlined Sales Tax. Exemptions
Some states refuse multi-state forms and insist on their own documentation. Before relying on any uniform certificate, sellers should confirm the destination state actually honors it. A certificate that looks complete but uses the wrong form for a particular state is essentially worthless in an audit.
Expiration, Validation, and Storage
Certificates do not last forever. Some states require annual renewal, others set expiration at three to five years, a handful have no fixed expiration. A certificate that was valid when collected can go stale without anyone noticing, especially in long-term vendor relationships where orders flow automatically. Sellers should track expiration dates and request updated certificates before the old ones lapse. An expired certificate discovered during an audit provides no protection.
Collecting a certificate is only half the job. The seller also has to verify the buyer’s information. Most state revenue departments run online portals where sellers can enter a tax ID and confirm the buyer’s account is active and in good standing. Running this check at the start of the relationship, and periodically afterward, catches problems like revoked registrations or closed businesses before they become the seller’s liability.
Certificates must be retained for a period that matches the state’s statute of limitations for sales tax assessments, which runs three to six years depending on the jurisdiction. Digital storage is the practical choice. It allows quick retrieval during audits, avoids lost paper, and makes it easy to link each certificate to specific invoices. If a seller cannot produce a valid certificate when audited, the state will assess the uncollected tax plus interest. Penalties for unpaid sales tax generally run from 5% to 25% of the amount due, and higher in cases involving fraud or intentional misuse of certificates.
Services Between Businesses
Most B2B tax conversations focus on tangible goods, but services carry their own complications. Roughly 41 states plus the District of Columbia do not tax services by default; they tax only the services specifically listed in their statutes. A handful of states take the opposite approach and tax nearly all services, with exceptions carved out for specific categories.
Common B2B services that end up on the taxable list include janitorial and cleaning services, pest control, equipment repair, telephone answering services, credit reporting, and landscaping. Professional services from attorneys, accountants, and physicians are among the least-taxed categories, though a few states do reach them. The same consulting engagement can be taxable in one state and exempt in the next.
Installation and repair labor adds another wrinkle. Many states exclude charges for installing tangible personal property from the tax base but still tax the parts and materials. When a service provider furnishes both, tax treatment often turns on whether the materials make up a significant portion of the total charge and whether the invoice separates labor from parts. Businesses paying for repair or installation work should ask for itemized invoices and check what their state actually taxes.
Software, SaaS, and Digital Products
Software sold between businesses is one of the messiest areas of B2B sales tax. No federal framework governs how states treat software, so the result is a patchwork driven by how the software is delivered and how the state classifies it.
As of late 2025, roughly 24 states tax Software-as-a-Service in some form. Some classify SaaS as a digital product, others as a data processing service, others as a non-taxable service. Delivery method matters. States that focus on whether software is downloaded or delivered on physical media often exempt cloud-hosted SaaS because nothing is transferred to the buyer’s possession. States that focus on function may tax it regardless of delivery.
B2B buyers sometimes get a break individual consumers do not. A few states exempt SaaS or reduce the rate when the buyer is a commercial enterprise using the software for business purposes. Others make no distinction. Because the rules change often and differ sharply, this is a category where nationwide sellers should invest in state-by-state research or automated tax calculation tools rather than generalizing.
Drop Shipping
Drop shipping creates a three-party puzzle. In a typical drop shipment, a retailer takes an order, then directs a separate vendor to ship the product to the retailer’s customer. Two sales happen at once: the vendor sells to the retailer at wholesale, and the retailer sells to the customer at retail. The question is which party collects tax and in which state.
If the vendor has nexus in the state where the goods are delivered, the vendor needs a valid resale certificate from the retailer to avoid charging the retailer tax on the wholesale price. What counts as valid varies. Some states accept a certificate from the retailer’s home state, others insist on one bearing a registration number issued by the destination state. If the retailer cannot provide the right certificate, the vendor has to charge tax on the wholesale transaction.
If only the retailer has nexus in the destination state, the retailer collects tax from the end customer. If neither party has nexus, no one may be obligated to collect, though the customer likely owes use tax. For businesses running drop shipping networks across many states, mapping which party has nexus in each destination is essential. Getting it wrong means either double taxation or uncollected tax that surfaces in an audit.
Equipment Leases and Construction Contracts
Leased Equipment
Businesses that lease equipment instead of buying it still face sales tax, but the timing shifts. For a standard operating lease, where the lessee returns the equipment at the end of the term, most states impose tax on each lease payment as it comes due. For capital leases that effectively transfer ownership, many states treat the transaction like a financed purchase and require the full tax to be paid upfront or with the first payment.
Some states let the lessor choose: pay tax when acquiring the equipment and skip collecting it from lessees, or buy the equipment tax-free under a resale certificate and collect tax on each lease payment. A lessee should confirm which approach the lessor is using, because it determines whether tax appears on the invoice.
Construction Materials
Construction contractors occupy an unusual position. In most states, a contractor who incorporates materials into a building or other real property improvement is treated as the end consumer of those materials, not a reseller. The contractor pays sales tax when buying the lumber, pipe, or concrete, and the charge to the property owner for the finished project is not a separate taxable sale.
The exception is a separated or “time and materials” contract, where the invoice breaks out materials from labor. In some states, this contract form makes the contractor a retailer of the materials and requires sales tax on the materials portion of the invoice. The practical difference between a lump-sum contract and an itemized one can shift who pays the tax and when. Businesses hiring contractors for large projects should understand how their state treats the contract form, because it directly affects the total cost.
Use Tax: When the Seller Doesn’t Collect
When a seller does not collect sales tax, because it has no nexus in the buyer’s state or the invoice slipped through, the buyer is not off the hook. Every sales-tax state also imposes a use tax on tangible personal property purchased without tax and then stored, used, or consumed in the state. The use tax rate matches the sales tax rate that would have applied locally.
Businesses are expected to track untaxed purchases through the year, self-calculate the use tax owed, and remit it on their regular sales and use tax returns, whether monthly, quarterly, or annually. It is easy to overlook, especially for companies making many small out-of-state purchases. Auditors know where to look, comparing purchase records against sales tax paid and flagging the gaps. Unpaid use tax accumulates fast, and states charge interest from the date the tax was originally due. Penalties for non-payment typically start at 5% and can reach 25% or more, with criminal exposure possible in cases of willful evasion.
Direct Pay Permits
Large buyers that cannot determine at the point of purchase whether an item will be used in a taxable or exempt way can sometimes qualify for a direct pay permit. A company that buys chemicals in bulk, for example, might use some in tax-exempt manufacturing and some in taxable facility maintenance. A direct pay permit lets the buyer skip paying tax to the vendor and instead self-assess the correct tax based on actual use, then remit it directly to the state.
Not every business qualifies. States that offer direct pay permits generally require the applicant to be registered for sales tax, maintain a place of business in the state, keep a clean filing history, and show that the inability to determine taxability at purchase is a genuine operational issue, not a preference for paying later. The permit does not cover purchases that are obviously taxable and does not substitute for a resale certificate. Vendors keep the direct pay permit on file and treat those sales as exempt, which also reduces their own audit exposure.
Fixing Past Mistakes: Voluntary Disclosure
A business that discovers it should have been collecting or paying sales tax in a state, but has not been, is almost always better off coming forward than waiting to get caught. Most states offer voluntary disclosure agreements that waive penalties and limit the lookback period to a set number of prior years, typically three to five. The back taxes and interest still get paid, but the penalty savings can be substantial.
The Multistate Tax Commission runs a Multistate Voluntary Disclosure Program that lets a business resolve obligations in multiple states through a single process. The MTC treats the applicant’s identity as confidential during negotiations; states know only a case number until a formal agreement is signed. In exchange for filing returns and paying back taxes for the lookback period, the state waives penalties and forgives liability for years before the lookback window.6Multistate Tax Commission. Multistate Voluntary Disclosure Program There is no cost to participate.
The catch: a business that has already been contacted by a state about an audit or assessment generally does not qualify for voluntary disclosure in that state. The window closes once the state comes knocking. Any business expanding into new states or reassessing its nexus footprint after Wayfair should look at voluntary disclosure sooner rather than later. The longer the gap between when the obligation arose and when the business comes forward, the larger the back-tax bill.