Forget the background check for a minute. What exactly are you going to say in the interview when you are asked the inevitable question "So Mr Someone - what did you exactly do between May and December 2003?"....If you say you did nothing - you come across as an idle cretin, if you say you built wells in Peru or did a sponsored cycle-ride across China, they will ask you why you didn't mention this before - and then dismiss you for being a lying, idle cretin. If you tell the truth and say you were a catalogue model for "Just 4 Boys" then they might stifle a laugh (or possibly find you more alluring) but they won't dismiss you... either during the interview process or later on...Now back to the background check. Basically your question is "can a background check agency really check my background?" I would suggest they can, they do and they will. Otherwise you would think their own integrity would be compromised... Unless you were stripping for tips in a Bradford boozer, you will probably have NI contributions, pension contributions, P45s - there will be an audit trail. And for a gap in the employment history - they MAY just concentrate on this...