CSEP application - can offer be attached or exactly contract is required?

[nastio]

Hi,
I am trying to figure out whether it is sufficient to attach only offer letter or exactly contract is required for the application?

[meself2]

I would not expect an offer letter to be sufficient.

Offer letter is what it is - an offer. You can accept or deny.
Contract is a legally binding agreement that gives you the job, on the basis of which (the job) you're eligible for the visa.

[nastio]

Thank you a lot for your response!