What's the difference between ECI and FDAP income?

ECI (effectively connected income) is US business income connected to a US trade or business — it's taxed on a NET basis at graduated rates (21% for corporations), with deductions allowed, and reported on a US return. FDAP (fixed, determinable, annual, or periodical income) is passive income like dividends, interest, rents, and royalties — taxed on a GROSS basis at a flat 30% withheld at source, with no deductions, unless a treaty lowers the rate.

How is the 30% FDAP withholding reduced?

Two ways. A tax treaty between the US and the recipient's country can reduce the 30% rate — often to 15%, 10%, 5%, or 0% depending on the income type. Separately, the portfolio interest exemption can bring qualifying interest to 0%. To claim either, the foreign recipient gives the US payer a valid Form W-8BEN (individuals) or W-8BEN-E (entities) certifying eligibility before payment.

What is Form W-8ECI used for?

A foreign person gives Form W-8ECI to a US payer to certify that the income is effectively connected with a US trade or business. That certification removes the income from 30% FDAP withholding — because ECI is instead reported and taxed on a net US return (Form 1040-NR or 1120-F). Without a valid W-8, the payer must withhold at the full 30% statutory rate.

What happens if I don't give my US payer a W-8 form?

The payer is required to treat the payment as FDAP and withhold at the full 30% statutory rate — and to remit that tax to the IRS. If you were entitled to a lower treaty rate or to net ECI treatment, you'd have to file a US return to recover the over-withheld amount. Providing the correct W-8 up front avoids the cash-flow hit and the refund paperwork.

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US Inbound Tax

ECI vs. FDAP: Net Taxation, 30% Gross Withholding, and the W-8 Forms That Decide

The same dollar of US income can be taxed at 21% net or 30% gross depending on one classification: effectively connected income or FDAP. The W-8 form your payer holds is what sets the rate.

SMAART Tax Team

February 24, 2026

7 min read