'I.R.S.' stood for 'International Record Syndicate' (or 'Independent Record Syndicate' on some early releases) and was started in the US in 1979 by Miles Copeland (brother of Stewart Copeland) as an American version of a group of punk and new wave labels that he operated in the UK under the umbrella name Faulty Products (a name that he later used for an I.R.S. sub-label in the US).
I.R.S. releases were distributed by A&M Records until 1985, by MCA Records until 1990, and finally by EMI (which bought the label in 1994) until the label folded in 1996.