HI I have a question about IBM verification i have worked 3 companies as of now and recently selected by IBM , but in my 3 companies my first company is no more now, so my question is while joining how many companies offer letters i need to submit ,whether 2 or all the 3 , please let me know as soon as possible.

Typically reference checks are against your most recent employer, in some situations if you have been with the most recent employer for a short time (lets say less than 6 months or so) you might be asked references from the one before. It also depends on how satisfactory your references.