Three resident years in a row keep you ordinarily resident for three tax years after moving to the US from Ireland. Taxes there still apply to your worldwide gains if you are Irish-domiciled, but not to your US pay.

Ireland has no seven-year rule for leavers or for gifts, but one capital gains relief turns on seven years of ownership. It covers land or buildings in Ireland or the EEA bought from December 7, 2011 to December 31, 2014. On a sale now, the exempt share is seven divided by the years you owned it, so at most seven-elevenths in 2026. The US does not follow the relief, so a US resident is taxed on the whole gain. Only the Irish tax on the rest of the gain earns a US credit.

Yes: the US-Ireland tax treaty is the convention signed at Dublin on July 28, 1997, replacing one from 1949. It has been in force since December 17, 1997, and has applied since January 1, 1998. A 1999 amending convention changed only Article 10(4), on dividends from US mutual funds (RICs) and real estate investment trusts (REITs). Its saving clause lets the US tax you as a resident under US law, apart from listed exceptions. Ireland keeps the same right over its residents. A separate 1949 convention covers Irish inheritance tax and US estate tax, but not gift tax.

Yes: US citizens living in Ireland pay tax to both countries. Ireland taxes them while they are resident there, and the US taxes its citizens on worldwide income wherever they live. The saving clause keeps that US right, with a foreign tax credit for Irish tax under Article 24. Under Article 18(1)(b), though, only Ireland may tax US Social Security paid to an Irish resident, even a citizen.

An Irish pension usually stays put until you can draw it, from 60, or from 50 on early retirement. Once you are a US resident, only the US taxes a private employer’s pension, and a PAYE Exclusion Order stops Irish withholding. A public-service pension stays taxable in Ireland under Article 19 unless you are a US citizen. No treaty article carries Ireland’s €200,000 tax-free lump sum into US law or defers US tax on the plan’s growth. Only visa holders may deduct contributions, for up to five calendar years, if they paid in just before arriving and the IRS accepts the plan.

Irish-domiciled ETFs are usually PFICs once you are a US resident, because a fund of securities meets the income or asset test. A fund set up as an Irish public limited company (plc) is a corporation under US rules. Other fund forms, such as an ICAV or unit trust, usually default to corporate status. Without an election, a sale’s gain is ordinary income. The part spread over your earlier US-resident years is taxed at the top rate plus interest. Each fund generally needs its own Form 8621 every year, and a qualified electing fund (QEF) election needs the fund’s PFIC Annual Information Statement.