I have very strong and clean background in my job history until recently. I got laid off last Nov. I started searching new jobs since Jan. Now I got the offer. During interview not much was asked about my last job from where I got laid off due to lack of work they had, but my previous experience was strongly matching with job requirement, however employer was not aware of my laid off and at the time I got offer, I have around 5 months of gap. Background check is about to start. I need advise as what should I do? Thanks
You should have volunteered the information during the interview, or given them a more accurate resume. "You didn't ask" isn't a good excuse for not conveying information which is relevant. At that time you could have mentioned very casually that the problem which had caused you to start looking for other work (not having enough work at your current job) came to its inevitable conclusions, etc. At that time, it wouldn't have been thought remarkable.
If there is some way you can matter-of-factly slip the information to them, in a casual conversation or an updated resume, you should be able to smooth this over. It may be that they won't care one way or the other especially if you don't seem to be hiding it.
You could even have presented it as an advantage ("I just wanted to let you know I have been laid off earlier than I anticipated and I am available whenever you want me to start..."). However, the five month gap kind of shoots that down now.
If they turn up the lay-off during the background check and ask "why didn't you say anything at the interview?" you may be able to get away with "sorry, didn't realize you were working off an old resume." I'd advise you to get your resume updated and put it out on linked-in or whatever sites you post your resume to, to make it obvious that you aren't trying to cover up your layoff...