Two layers of withholding
There are two separate points where tax can be withheld on a dividend:
- Level 1 — inside the fund: when a US (or other foreign) company pays a dividend to the ETF, that country withholds tax before it reaches the fund.
- Level 2 — fund to you: when the ETF pays you, your country (and sometimes the fund's domicile) may withhold again.
UCITS ETFs are powerful mainly at Level 1.
Why 15% beats 30%
The US standard withholding rate on dividends to foreigners is 30%. But the US–Ireland tax treaty cuts it to 15% for Irish-domiciled funds. Since most global and US-equity UCITS ETFs are Irish-domiciled, they collect US dividends at 15% rather than 30% — and crucially, an Irish-domiciled ETF pays no further withholding when it distributes to you.
Physical vs synthetic replication
A subtle twist: some UCITS ETFs use synthetic replication (swaps) for US equities and can, in specific cases, achieve an effective 0% withholding on US dividends — because the swap counterparty, not the fund, holds the stocks. This can edge out even the 15% physical funds, at the cost of added counterparty complexity. For most investors a low-cost physical Irish-domiciled fund is the sensible default.
What you still owe at home
None of this removes your own domestic tax. Whatever the fund distributes (or accumulates) is still taxable under your country's rules. See exactly how in the Tax Assessor, and read UCITS vs US ETFs for the estate-tax angle.
Dividend, capital-gains and withholding rates where you live.