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Late 2025 • Economic nexus • P.L. 86-272 erosion • SSF + market sourcing • GRTs • SALT addbacks • 482 • GILTI/FDII (2026) • BEAT • Withholding

C Corp SALT & International Tax (2025): the compliance map after Wayfair—and the global rules after OBBBA

For multi-jurisdictional C corporations, the modern risk is less about “where you have offices” and more about “where you have customers.” States have matured economic nexus standards that extend beyond sales tax into income, franchise, and gross receipts regimes—while P.L. 86-272 protection is increasingly fragile for digital commerce. Meanwhile, international planning is dominated by transfer pricing discipline and OBBBA-driven shifts to GILTI/FDII and BEAT. :contentReference[oaicite:0]{index=0}

Educational overview only — not legal/tax advice.

Contents

  1. State nexus in 2025: economic nexus maturity
  2. P.L. 86-272: why “cookies” and web features can void protection
  3. Gross receipts taxes: why losses don’t mean zero tax
  4. Apportionment & sourcing: SSF, market sourcing, COP collisions
  5. Nowhere income: throwback and throwout rules
  6. Federal–state interaction: SALT deduction, addbacks, PTET traps
  7. International: transfer pricing, GILTI/FDII shifts, BEAT, withholding
  8. A practical 2025 operating playbook

1) State nexus in 2025: economic nexus is no longer “just sales tax”

The post-Wayfair model has expanded: states increasingly assert corporate income/franchise tax jurisdiction based on in-state receipts alone—even without employees, property, or offices. Thresholds differ by state and can include special unitary-group aggregation rules, so receipts tracking must be state-specific and continuous. :contentReference[oaicite:2]{index=2}

2) P.L. 86-272: the “digital solicitation” safe harbor is eroding

P.L. 86-272 historically shielded sellers of tangible personal property from state net income taxes if their in-state activity was limited to solicitation and orders were approved and shipped from out of state. The modern problem: common web behaviors (customer support chat, certain cookies, post-sale features, job application portals) can be characterized as non-ancillary business activity—voiding protection in states adopting aggressive guidance. :contentReference[oaicite:3]{index=3}

Practical conclusion

If you run a modern commerce site, assume P.L. 86-272 protection may be unavailable in key states and build your nexus posture accordingly. :contentReference[oaicite:4]{index=4}

3) Gross receipts taxes: cash-flow risk even when profit is negative

Several jurisdictions impose taxes measured by receipts (or modified receipts) rather than net income. These regimes can be especially punitive for fast-growing, low-margin companies because deductions for operating costs may be limited or nonexistent. :contentReference[oaicite:5]{index=5}

4) Apportionment & sourcing: SSF makes “where the customer is” decisive

The dominant state trend is single sales factor (SSF) apportionment, paired with market-based sourcing for services and intangibles. That combination shifts the tax base toward destination states (where customers receive the benefit), and it raises double-tax/nowhere-income risks when market-based and cost-of-performance rules collide across different states. :contentReference[oaicite:6]{index=6}

5) Nowhere income: throwback and throwout rules reclaim untaxed sales

Where a corporation is not taxable in a destination state (including due to P.L. 86-272 claims), origin states may “throw back” those sales into their numerator, or “throw out” untaxed sales from the denominator—raising effective apportionment percentages. In some structures, creating nexus in a destination state (even if tax is small) can reduce overall liability by preventing throwback. :contentReference[oaicite:7]{index=7}

6) Federal–state interaction: the C Corp SALT advantage (and the addback reality)

Unlike individuals, C corporations generally can deduct state and local income/franchise taxes federally. But states typically require addbacks of taxes “on or measured by income” when computing their own state tax base—so the benefit is primarily federal, not state-level. The report also highlights how PTET elections (designed for pass-through owners) can create awkward outcomes when a C corp is a partner. :contentReference[oaicite:8]{index=8}

7) International: transfer pricing discipline + OBBBA-driven system changes

Cross-border planning is dominated by three pillars: (1) transfer pricing (Section 482) with contemporaneous documentation to mitigate penalties, (2) minimum-tax style regimes like BEAT (including services-cost-method nuances), and (3) the evolving GILTI/FDII framework—renamed under OBBBA with meaningful parameter changes heading into 2026. Add in withholding on U.S.-source FDAP payments, treaty access constraints, and portfolio interest rules, and international tax becomes a documentation-first sport. :contentReference[oaicite:9]{index=9}

Transfer pricing: the “best method” + 30-day response reality

The report emphasizes contemporaneous documentation timelines and penalty exposure—treat TP files like a deliverable that’s “always ready,” not something to assemble after an exam notice. :contentReference[oaicite:10]{index=10}

BEAT: routine services can be a leverage point

Payments eligible for services-cost-method treatment can reduce base-erosion exposure when properly scoped and documented. :contentReference[oaicite:11]{index=11}

A practical 2025 operating playbook

  • • Implement automated state receipts tracking (sales + services + digital) and alert on threshold crossings.
  • • Maintain a state “policy matrix” for sourcing rules, SSF weights, throwback/throwout, and GRT regimes.
  • • Treat P.L. 86-272 as a position that requires website-activity review and evidence—not a default assumption.
  • • Build a VDA remediation workflow for late discoveries, and coordinate sales-tax and income/franchise exposure together.
  • • Align transfer pricing narratives with operational reality (functions/risks/assets) and keep documentation contemporaneous.
  • • Map 2026 international “cliffs” (GILTI/FDII parameters, BEAT rate) into multi-year cash tax forecasts.
  • • Standardize withholding + treaty onboarding (W-8 collection, LOB checks, portfolio interest eligibility).

The report’s core message: success requires a cohesive strategy where state nexus monitoring and international documentation operate as one system. :contentReference[oaicite:12]{index=12}