Cost-of-performance sourcing assigns receipts from a service sale to the single state where the seller performed the greatest share of the direct-cost work behind that sale. Roughly ten states still use some form of this method for their corporate income tax; the rest have moved to market-based sourcing, which looks at the customer’s location instead.1Multistate Tax Commission. Review of MTC Model Sales Receipts Sourcing and Special Industry Regulations Because both systems coexist, the same service contract can be sourced to different states by different taxing authorities, so the mechanics matter.
How the Rule Assigns Service Revenue
The foundation is Section 17 of the Uniform Division of Income for Tax Purposes Act, drafted in 1957 and carried into the Multistate Tax Compact.2Multistate Tax Commission. Article IV – UDITPA Section 17 sources sales other than tangible personal property to the state where the “income-producing activity” is performed. When the activity crosses state lines, the sale goes to whichever state has a greater proportion of that activity than any other single state, measured by costs of performance.3Multistate Tax Commission. Multistate Tax Compact
An income-producing activity, under the Multistate Tax Commission’s model regulations, is any transaction or activity the taxpayer engages in during the regular course of business to generate a particular item of income. It is analyzed one item at a time. It covers employee services, the use of tangible property such as equipment and office space, and the use of intangible property such as proprietary software or patents.4Multistate Tax Commission. Model General Allocation and Apportionment Regulations
The analysis focuses entirely on the seller’s operations. A consultant who researches and writes a report in one state and delivers it to a client in another has performed the income-producing activity where the report was prepared. The client’s location does not enter the calculation. Auditors verify the position using time records, equipment usage logs, and similar documentation that ties work to a physical location.
The Greater-Proportion Rule
Standard UDITPA sourcing is all-or-nothing. Once direct costs are mapped by state, the state with a greater proportion of the activity than any other single state receives 100% of the receipts in its sales factor numerator.3Multistate Tax Commission. Multistate Tax Compact This is a plurality test, not a majority test. If 35% of direct costs sit in one state, 30% in a second, and the remaining 35% split among others, the first state claims everything.
The result can be counterintuitive. A project spanning five states can push all $2 million of contract revenue to a state where only $400,000 of work happened, simply because no other single state had a higher share. For firms with distributed workforces, small shifts in where employees sit can swing the outcome hard.
What Counts as a Direct Cost
Costs of performance means direct costs, determined consistently with generally accepted accounting principles and the accepted practices of the taxpayer’s industry.4Multistate Tax Commission. Model General Allocation and Apportionment Regulations Only costs directly tied to performing the specific service count. The main categories:
- Wages and compensation for employees who perform the service work, allocated to the location where each employee actually works.
- Specialized supplies, software licenses, or equipment used for the engagement.
- Direct overhead such as rent and utilities for the space where the work happens, to the extent attributable to the specific project.
- Payments to agents or independent contractors for services that directly produce the income. The MTC model regulations treat these payments as part of the taxpayer’s own costs of performance.4Multistate Tax Commission. Model General Allocation and Apportionment Regulations
Excluded costs include executive salaries, human resources, accounting, advertising, and other expenses that keep the business running but are not tied to performing a specific service. Marketing is out because it helps win contracts rather than fulfill them. The line between direct and indirect overhead is genuinely blurry for many professional services, and that is where audits most often land.
Every dollar of direct cost has to be assigned to a location. Internal accounting records, W-2 wage allocations, and project-tracking systems supply the data. The geographic breakdown drives the sourcing result.
Variants Among the Cost-of-Performance States
Not every state applies the rule identically. Some use a “predominant” cost-of-performance test, which functions closer to a true majority requirement. A handful use a proportional method that sources a fraction of the revenue to each state based on its share of direct costs, avoiding the cliff-edge outcomes of the all-or-nothing test at the cost of extra calculation. States that keep the standard rule expect documentation showing both that your state had the highest share and that you properly excluded indirect costs.
How Market-Based Sourcing Differs
Cost-of-performance sourcing looks at where the seller worked. Market-based sourcing looks at where the customer received the benefit. Under the MTC’s revised model regulations, amended in 2014, service revenue is sourced to where the service is delivered, generally meaning the taxpayer’s market rather than the location of the taxpayer’s employees or property.1Multistate Tax Commission. Review of MTC Model Sales Receipts Sourcing and Special Industry Regulations
Over three-quarters of states with corporate income taxes now apply market-based sourcing.1Multistate Tax Commission. Review of MTC Model Sales Receipts Sourcing and Special Industry Regulations The gap between the two methods can be substantial. A software-as-a-service company that hosts servers and employs developers in one state while serving customers nationwide keeps most receipts in the server state under cost-of-performance rules but spreads them across the customer base under market-based rules. Remote employees widen the gap further: a home office can pull revenue into a state where the company has no customers at all under cost-of-performance rules, while market-based rules ignore the employee and follow the client. Multistate businesses commonly run parallel sourcing analyses, and the same revenue can end up claimed by one state under one method and another state under the other.
Nexus Consequences of Performing Work in a State
Cost-of-performance sourcing creates a feedback loop with nexus. Performing services in a state can establish enough presence to trigger a corporate income tax filing obligation there, and the same activity that creates the nexus also pulls receipts into that state’s sales factor. Each new location where work gets done is a potential new filing obligation.
Service companies do not get the protection of Public Law 86-272, the federal statute that limits state taxation of interstate commerce. That law shields businesses whose only in-state activity is soliciting orders for tangible personal property shipped from outside the state.5Office of the Law Revision Counsel. 15 USC 381 – Imposition of Net Income Tax Selling services, licensing intangibles, and delivering digital products all sit outside its scope.6Multistate Tax Commission. Statement on P.L. 86-272 A consulting firm whose only tie to a state is one employee working from a home office there has no federal shield against that state’s income tax.
Several states have adopted factor-presence nexus thresholds that trigger filing obligations based on set dollar amounts of in-state payroll, property, or sales. When a remote employee’s compensation crosses the payroll threshold, the employer picks up a filing requirement without any deliberate expansion into that state.
Throwback and Throwout Traps
If cost-of-performance rules assign receipts to a state where the seller has no tax obligation, that revenue can become “nowhere income” that escapes taxation. Some states close this gap with throwback or throwout rules.7Multistate Tax Commission. Notes on Throwback Rule
A throwback rule reassigns the untaxed receipt to the state where the work originated, inflating that state’s sales factor numerator. A throwout rule removes the untaxed receipt from the sales factor denominator, which raises the effective apportionment percentage for every other state. Both mechanisms increase the tax burden, through different math. These rules were originally built for sales of tangible goods, and they interact with service sourcing in ways that catch companies off guard: a service provider that sources revenue to a low-tax state under cost-of-performance rules may find the receipt thrown back to its home state if it lacks nexus in the destination.
Why Sales Factor Weighting Magnifies the Result
How much service sourcing matters depends on how the state weights its apportionment formula. UDITPA originally weighted property, payroll, and sales equally at one-third each. Today most states with a corporate income tax weight the sales factor heavily, and roughly 34 of the 44 states that tax corporate income use a single-sales-factor formula where the sales factor is the entire calculation. In those states, service sourcing is effectively the whole apportionment question.
Where a three-factor formula still applies, a sourcing error in the sales factor gets diluted by property and payroll. Under a single-sales-factor formula, every dollar of service revenue shifted between states moves a proportional slice of taxable income with it. That magnification is why service-sourcing has become the most contested area of state corporate tax audits.
Records You Need to Defend the Position
The burden of proof on apportionment generally falls on the taxpayer. If a state auditor challenges your sourcing, you need contemporaneous records showing where the income-producing activity happened and how you calculated costs by location. Without adequate books and records, the taxing authority has broad discretion to estimate an assessment.
Useful records include project-level timekeeping systems that track hours by employee and location, equipment and software usage logs tied to specific engagements, and accounting records that allocate direct costs to projects before those costs roll into general ledger totals. Contemporaneous is the operative word. Reconstructing this data after an audit notice arrives is much harder than capturing it as the work happens, and auditors treat after-the-fact allocations with skepticism.
Companies operating in both cost-of-performance and market-based states carry an added record-keeping load: they need to track where the work was performed for the first group and where the customer received the benefit for the second. The cost of maintaining parallel tracking is real, but small next to the cost of losing an audit.