Thanks Thierry for your help. I went to Configuration -> Users - > Click on the user -> Modify ->Go to Access rights tab, but I didn't see any "Authorized Companies" (I set the language to english)

Ok, I turned to English (I'm french) and the right sentence is "Allowed Companies"

I still do not see this label on the tab..I see the company to which the user is attached on the top of the tabs but that's it! I'm using openerp v7 to recall the context i fit can help

Oh, I see, maybe this is because I enabled Multi Company. Sorry, but I don't know how-to help more.

Ok I set to multi-company, double checked that the users were associated to the apropriate company, and edited a new "Default Company per Object" with the object Account, and still see "Your company" on the purchase receipt...

Ok I found something that could help. When I go to my profile preferences (top right corner of the screen) the window opens and I can only see the label 'Default point of sale', but it should show as well 'Company' label with a drop-down list to chosse the company of the user. Do you have any idea I don't see this label + drop-down box ?