The statutory calculation changed after 2025
For tax years beginning after December 31, 2025, section 250 generally allows a domestic corporation a deduction of 33.34 percent of foreign-derived deduction eligible income, or FDDEI, subject to the applicable requirements and limitations. The 2025 law changed the former FDII framework, including removal of the deemed tangible-income-return calculation and changes to deduction-eligible income. An old spreadsheet using the prior percentage and tangible-asset return should not be rolled forward without review.
Foreign customer revenue is not automatically FDDEI. The corporation must establish eligible income, qualifying foreign sales or services, foreign use or location, properly allocable deductions, and applicable exclusions. The rules include taxable-income limitations and other interactions. Certain property dispositions were excluded by changes effective after June 16, 2025, a different date from the 2026 calculation changes. September 2026 proposed regulations address aspects of those exclusions; proposed rules must be distinguished from enacted law and any permitted reliance conditions. This guide concerns the operating-income deduction, not choosing a corporate entity or selling the business. Use the rules applicable to the actual year and transactions before forecasting a reduced rate.
Compute a hypothetical supported FDDEI deduction
Assume a domestic C corporation has $500,000 of supported FDDEI in a tax year beginning in 2026. Assume it has sufficient taxable income, no other section 250 category complicates the limit, and all eligibility and expense-allocation requirements are satisfied. Applying 33.34 percent gives a deduction of $166,700. The remaining simplified taxable amount is $333,300.
At the ordinary 21 percent corporate rate, tax on that amount is $69,993, approximately fourteen percent of the original $500,000. Without the deduction, tax would be $105,000, a difference of $35,007. These figures do not establish that every dollar of foreign sales receives a fourteen-percent rate. If only $300,000 of an initially assumed $500,000 actually qualifies, the deduction and tax benefit must be recomputed on that smaller supported amount. This example also excludes state conformity, credits, losses, and other return interactions. The owner should see the eligible income calculation and limitation, not merely a headline effective rate attached to gross export revenue.
Rebuild the transaction and expense file
Retain customer status, delivery destinations, foreign-use evidence, service recipient or property location, contracts, invoices, and any related-party analysis required by the applicable rules. Separate qualifying and nonqualifying transactions and reconcile both to revenue. A foreign billing address alone may not establish the required use or service facts.
Map expenses and deductions to the eligible-income calculation under current law, including the amended treatment of interest and research expenditures where applicable. Identify excluded categories and property dispositions rather than applying the percentage to all international revenue. Preserve the statutory effective-date analysis for transactions after June 16, 2025, and tax years beginning after 2025. If relying on proposed guidance, document the actual reliance conditions and consistent application rather than describing the proposal as final. Keep the old calculation for prior years but create a reviewed current-year version. Reconcile the resulting deduction to the return and any applicable form instructions. The file should allow another preparer to trace qualifying income, allocated costs, exclusions, limitations, and the final deduction without reconstructing customer geography from scratch.
Use the benefit in pricing only after qualification
An expected FDDEI deduction can affect a corporation's after-tax margin, but the business should not discount export bids based on unsupported gross revenue. Compare the operating profit after all required costs, then apply the supported deduction and limitations. A sale can have a foreign customer yet fail the particular qualification rules.
Update the forecast when customer use, delivery location, contract scope, or the corporation's taxable income changes. Review current guidance before filing because the 2026 proposed rules may develop further. Keep federal and state results distinct. The practical outcome is an export-income forecast rebuilt for the enacted 2026 regime, with the deduction tied to substantiated income rather than an outdated FDII percentage or an assumption that international receipts automatically receive a preferred rate. Report gross foreign revenue, allocated operating costs, supported FDDEI, and the deduction as separate projection lines. That bridge helps reviewers identify whether a revision came from customer eligibility, expense allocation, or the taxable-income limitation.
Sources & further reading
Consult the original guidance and its effective dates. These references support the educational discussion; their application depends on the specific facts.