Yup. I do that. I've found it works much more effectively than late fees.
People love getting a bargain. Some financial departments are setup so that they will always take the cheapest option.
Make the cheapest option the one that gets you paid up front. Made my life much simpler.
You also get some of the advantages - to channel patio11 for a moment - of "charge more". Your base day rate - the one that anchors your true value - is the "expensive" one that factors in the cost of late payment to you.
