Joining a new psu

The way you worded your query, you are not able to convey problem.

What was the reason that you suppressed the information about your previous contractual employment?

If you have any specific reason then you can furnish that in your explanation reply if you are served with show cause notice, if any.

During online application time i was not joined that contract job, so not given in online application. During interview time i have completed 2 month.At that time i have not given details in interview form.at that time i think it is not relevant for my job role.during joining time i completed 8 months contract. I did not mentioned in joining form also.i have releiving letter from contract job. What happens if current employer finds it.i have no issue with previous employer

You have a relieving letter from the contract job and it may not lead to complications.

To my knowledge, PSUs do not have any procedure of back ground vertification.