I Just Get an Invoice Signed and ask if they have any q's, if not its good day, see ya next time! My Sales staff also does follow up calls on every service we performe!!!
We do a lot of work with the Construction Industry and absolutely have a Site Super or Project Manager sign off as "Work completed in a acceptable manner. No further work required". And signed off per unit when it involves multi-units. In new construction, the cleaning work is typically at the end of the project, and worse... the end of the budget. Sometimes it's "be first... or be too late".
I hand deliver invoices monthly on commercial accounts. During that time, we discuss job perforance and any "issues" that we might be having. Most often it's just some friendly chat, and we end up just talking about fishing and stuff... about 85% of the time, i get a new lead to another job.
Customer Relations is Great!
Once the job is finished I go around the job site with the customer and verify if he's satisfied with the work done, than I ask for a signature. I call back the customer within 2 weeks to make is sure everything is ok with him!
If I went back to every job I did to check on it I would lose have a week.