HarryC wrote:But they can do what they like if they find anything suspicious.
Another point is, i dont think they will call employer because all these checks would had been done, before the person got ILR !!
Agree with your first point, in that I believe they will only investigate if they see something that doesn't add up as true. On the second point however I'd have to disagree. I believe the HO will conduct the necessary checks (note that here I do not mean that they will call every single employer you have listed) irrespective of the fact that they may have done the same for your ILR. The reason being the requirements for naturalisation would be different to those for ILR, in addition to that immigration rules keep evolving, so what may have been valid when your ILR was granted may no longer be so for naturalisation as a result of subsequent changes. E.g. The Good character requirement changes that came into effect in December 2014.
One other point to be noted is that the HO have made mistakes in the past when granting visa extensions, ILR, if you read the experiences posted in the T1G/ILR forum you can see recent refusals due to deception which were not caught during the initial application stage, but discovered later. With the current checks for naturalisation being what they are, my sense is that they will check an applicants history (Immigration, Criminal record, HMRC, Other Government agencies etc...) going back 10 years, irrespective of any checks done before to ensure they don't miss anything a second or third time around.