Students who took part in the J1 visa programme last year could be entitled to a refund of over €600.
Taxback.com says around half of the 30,000 students who took part in the J1 programme have yet to claim their tax refund.
It says the deadline to submit their claim is April 17th.
They could be due refunds of around €645 - it says it could be the last year they get the tax back due to changes by President Donald Trump.
"I suppose it would be disappointing if a tax refund wasn't availble to Irish students anymore but our main concern at the minute is that the J1 visa keeps going and there are 150,000 students that have gone on J1 visas to the US since the programme came in," said USI President Michael Kerrigan.
"Students find it very beneficial and it's not something we would like to lose and that's our priority for now."