>Situation: I visit a customer. That customer paid for a given numbers of hours for on-site support. To make everything very clear I'd like to have something to certify what was done, when, how long...
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>This way I have a proof if at one point that customer say that I did'nt respect my engagement in all my visits.
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>So what kind of documents do you guys have to control this?

In my office back home, we had a workorder form, which was to be filled manually (as it made a copy). It'd had customer's identity, my identity, what was done (up to half a page of text), transportation data (i.e. kilometers, even when I came by bicycle, or modem time when it was remoted), and (most important) the payment type - which would be something like a radio button group on paper: a) under warranty, b) maintenance contract, c) user ordered. Maybe there was one more choice there, can't remember now.

This was something we'd write at the end of the visit, and had the user read and sign it. We had no complaints.