I'm curious to see what others are doing as for billing for extra items which you wouldn't normally itemize on the bill to the customer. For instance, do you add a percentage to cover small things like staples, wood screws, wire connectors, etc? Or do you bill them out separately, or roll them into your markup? What about consumables like saw blades, grinding disks, drill bits, etc? How about a fuel surcharge?
What I've been doing is getting a rough idea of small stuff we've used and charge it separately under "misc. supplies". Any feedback would be appreciated.
"Will it be cheaper if I drill the holes for you?"
In part, it depends upon the nature of your business, and the terms of the agreement you have with the customer.
If I'm doing work T&M, I will have a figure on my worksheet for "shop supplies."
Distant jobs will have a 'travel charge,' stipulated in advance. Charges for rentals, subbing to other trades, etc., will be spelled out in most cases.
Communication, and trust, is critical. It is too easy to undermine a relationship by presenting a bill far in excess of what the customer is expecting. I need only think back to the $29 tire that cost me $75.... I haven't been back there since (even though other shops were selling similar tires for $75, at last they didn't post a 'low' price!)