There is a right time to do everything, and so it is with invoicing. A few years ago I was working in publishing company as a software developer where I built an application for printing direct marketing sales notes. We would be printing these notes once a week and we were sending them to our clients. We were tracking reply rate and after many months of experimenting (sending always the same layout and similar message) we realized we were selling much more on one particular day.
It was Tuesday. Like no other day, Tuesday was best performer regarding requests from people to respond. Tuesday outperformed Friday by 930%! It did not matter if it was summer, winter or holiday season, Tuesday was always better than other days. From that moment on, we decided only to deliver direct mail on Tuesday and it payed off.
Just after we made a conclusion we will be always delivering on Tuesday, I remember reading words from Duško Radović (a Serbian poet and writer) saying:
Tuesday is the most modest day of all, it is so inconspicuous it could go without name. The day after Monday or the day before Wednesday. Monday is to talk about last week and arranging impressions. Wednesday is the real beginning of a new week. Tuesday is somewhere in between, like a storage room for items that aren’t frequently used. Tuesday is February of months.
It was funny and true and it turned out to be doing amazing things to our sales.
Later on, I did the same test when running my own software development company. I tested it with sending invoices to our clients and it gave me the same results. Tuesday was by far the best day to send invoice.
If invoice would be sent on Tuesday we would get payment during that week. If it was sent on Friday, the same client would make a delay for two or three weeks. This puts you and the client in difficult position as you have to threat them like a non-paying customer. So choose when to send your invoice wisely.
Final note: Sending the invoice in the morning, just after the beginning of the working hours is usually the best time. You’ll have the most chance to be on the top of the inbox.