Ethics - written confirmation from employer or not ?


I think I have been confused since level I with this topic. Can someone tell me what is the exact situation when we have to seek for the following :

  • Receive written confirmation from employer and other side

  • Receive written confirmation from the employer only

  • Receive oral confirmation

  • Just annouce it without receiving confirmation

If i am not wrong, the last one is when we receive a gift from a client regarding past resutls (but not influencing future agreement). In this case, we just have to announce it…but not 100% sure.

Thanks for your help !