I travel to the US several times a year using an ESTA visa. ESTA (Electronic System for Travel Authorization) rules change from time to time, but the most recent changes will cause headaches for some people. As of April 1 2016 you will need an “e-passport” to be able to avail of the waiver.
I recently replaced my Irish passport, so I’m not impacted, but I had an ESTA number associated with my old passport:
Effective April 1, 2016, the United States requires a valid e-Passport (passport with a chip) to travel to the United States under the Visa Waiver Program. You are receiving this email because your passport has been identified as a non e-Passport or it was issued prior to your country of citizenship’s issuance of e-Passports. Your ESTA application is cancelled due to this new travel requirement.
You will need an e-Passport to travel under the Visa Waiver Program or you may obtain a non-immigrant visa from a U.S. Embassy or Consulate in your non e-Passport. Once you obtain an e-Passport, you may re-apply for ESTA. The cancellation does not affect your future ESTA status. For more information regarding travel requirements, visit www.cbp.gov/travel.
Ireland started issuing the biometric e-passports that are compatible in October 2006, so while the number of Irish passport holders this change impact isn’t “huge” it would still be significant. My old passport wasn’t due to expire until late July 2016, though I replaced it back in February, as it was physically damaged and was causing me headaches with some trips. (It’s a bad sign when they politely suggest you need a new passport at passport control in Dublin!)
If you don’t have an e-passport you’ll need to get a visa for travel to the US. More information on the US embassy’s site.