Why Pass-Through Entities Commonly Have State Income Tax and Nonresident Withholding Exposure

Pass-through entities, including partnerships, S corporations, and LLCs taxed as either, are often thought of as simple from a state tax perspective: the entity itself generally does not pay federal income tax, and the income "passes through" to be taxed at the owner level. In practice, that simplicity is deceptive. Because states each have their own rules for taxing pass-through income, and their own requirements for withholding on behalf of nonresident owners, pass-through entities frequently accumulate state income tax and withholding exposure that goes unnoticed for years.

The Core Problem: Multi-State Owners and Multi-State Activity

A pass-through entity does not need significant multi-state operations to create multi-state tax exposure. Exposure can arise from either side of the equation:

• The entity itself does business in multiple states, whether through employees, offices, inventory, or, increasingly, economic nexus standards tied to sales volume alone.

• The entity's owners live in different states than the entity operates in, meaning even a single-state business can create nonresident filing and withholding obligations simply because one or more owners live elsewhere.

Because these two sources of exposure are independent of each other, a business can be highly compliant in evaluating one and still miss the other entirely. A company that carefully tracks where it has economic nexus for entity-level tax purposes may never separately evaluate whether its ownership group is entirely composed of in-state residents, and vice versa.

Reason One: States Tax Pass-Through Income Differently

Unlike the relatively uniform federal treatment of pass-through entities, states vary widely in how they tax this income, which creates room for gaps.

• Some states impose an entity-level tax on pass-throughs directly, separate from taxing the owners. This is separate from the pass-through entity tax election the state may offer.

• Other states rely solely on taxing the owners directly, requiring the entity to determine how income should be sourced and apportioned to each state where the entity has nexus, and then flow that information out correctly to each owner.

• Composite return rules differ significantly. Many states allow, or require, a pass-through entity to file a composite return on behalf of its nonresident owners, but the rules governing who must be included, what election is required, and what the entity's obligations are if a composite return is not filed vary considerably from state to state.

Because there is no single, uniform framework, a compliance approach built around one state's rules does not translate cleanly to the next, and gaps tend to accumulate as the entity expands into new states without fully rebuilding its analysis each time.

Reason Two: Nonresident Withholding Requirements Are Easy to Miss

Many states require a pass-through entity to withhold tax on income allocable to nonresident owners, functioning much like payroll withholding does for employees, but for owner-level income instead. This creates exposure for a few consistent reasons:

• The obligation exists at the entity level, not the owner level. Even if an individual owner is fully current on their own personal income tax filings in their home state and in the states where the entity operates, the entity itself can still be out of compliance if it failed to withhold and remit tax on that owner's behalf.

• Withholding thresholds and exemptions vary. Some states exempt owners who are already filing directly, or who have elected to be included in a composite return, from separate withholding requirements. If an entity assumes such an exemption applies without confirming it in each state, it can inadvertently skip a withholding obligation it was actually required to satisfy.

• New owners and ownership changes are not always flagged for tax purposes. When a new partner or shareholder is admitted, the tax function is not always looped in immediately, especially in businesses where ownership changes are handled primarily by legal or HR. If the new owner is a nonresident of a state where the entity operates, that can trigger a new withholding obligation that goes unnoticed until a return is prepared, or not noticed at all.

• Withholding is often based on estimated, not final, allocations. Because withholding is typically due throughout the year, based on estimates of allocable income, entities can underwithhold if income is heavily weighted toward the end of the year or if a significant transaction occurs that was not anticipated when estimates were set.

Reason Three: Nexus for Entity-Level Purposes Expands Faster Than Compliance Processes Adjust

Even when a pass-through entity has a reasonably solid handle on nonresident withholding for its existing owner base, the entity-level nexus picture tends to shift faster than internal processes account for.

• Economic nexus standards apply to income tax, not just sales tax. Many people associate economic nexus primarily with sales tax following Wayfair, but a number of states have also adopted, or already had, economic nexus standards for income tax purposes based on sales, payroll, or property thresholds. A business that has not crossed a sales tax threshold in a state may still have crossed the income tax nexus threshold, particularly since state income tax nexus thresholds are sometimes lower.

• Remote work has expanded nexus footprints without formal expansion decisions. A pass-through entity that never intended to "expand" into a new state can nonetheless create nexus there simply because an employee or partner works remotely from that state, sometimes without the tax function being aware the arrangement exists.

• Apportionment obligations follow nexus, even without a physical location. Once nexus exists in a new state, the entity generally needs to begin apportioning income to that state and flowing the appropriate share through to its owners, a step that is easy to miss if the new nexus was never formally identified or communicated internally.

Reason Four: Owner-Level Compliance Is Often Assumed, Not Verified

A recurring pattern in pass-through entity exposure is the assumption that if the entity provides accurate K-1s, or their state equivalents, the owners will handle their own compliance from there. In practice, this assumption breaks down in a few ways:

• Owners may not file in every state where they have a filing obligation based on the K-1 information provided, particularly for smaller allocations, and the entity generally has no visibility into whether that filing actually happened.

• The entity's own withholding and composite filing obligations exist independently of what the owner ultimately does. Even if an owner files and pays tax directly, the entity can still be assessed for failing to withhold or file a composite return if it did not meet its own separate obligation, creating a risk of the same income being taxed, and penalized, more than once if not carefully coordinated.

• Multi-tier ownership structures compound the problem. When a pass-through entity's owner is itself another pass-through entity, tracing withholding and filing obligations through multiple tiers to the ultimate individual or corporate owners adds a layer of complexity where gaps are especially likely to develop unnoticed.

What This Means in Practice

Because the sources of exposure are numerous and often independent of one another, addressing pass-through entity state tax risk generally requires looking at more than the entity's own physical footprint. A thorough review typically involves confirming entity-level nexus across all relevant tax types, verifying the residency of every owner in the current ownership group, reviewing withholding and composite return elections state by state, and tracing obligations through any multi-tier ownership structures. Where historic gaps are identified, and depending on the dollar amounts and number of periods involved, a voluntary disclosure agreement is often available as a way to resolve the exposure with a limited lookback period and reduced penalties, similar to the process used for sales tax or gross receipts tax exposure.

The Bottom Line

Pass-through entities accumulate state income tax and nonresident withholding exposure not because of any single mistake, but because the exposure has two independent sources, the entity's own multi-state activity and its owners' residency, layered on top of state rules that vary significantly and change frequently. Because no single internal function typically owns this issue end to end, it is worth periodically stepping back and evaluating both sides of the equation together, rather than assuming that solid income tax compliance in the entity's home state, or accurate K-1 preparation, means the full picture has been addressed.

This article is for general informational purposes and does not constitute legal or tax advice. Businesses should consult a qualified state tax advisor to evaluate their specific ownership structure and multi-state exposure.