The moment the job's and Your customer is satisfied, get the sign off electronically and send the invoice on the spot.
Having a signature on the spot is just no substitute. Everything is fresh in the minds of You and Your customer, You both agree and the invoice is exactly what they expect, moments after approval.
The benefits for technology and automation in business aren't more clear than when they help get cash flowing. Speed, elegance and simplicity mitigate all the risk in a transaction that's fundamental to to good business. The invoice app is a powerful link in one of Your most vital communication chains.