This calculates a monthly running total for each month, and displays the months on top of each other. It's useful to see if there's a monthly "curve" in your business, to compare monthly revenue streams and their variation, and to see how you're doing in the current month against previous months.

Note, the SQL query in this is somewhat "heavyweight"... it runs a subquery for each day and may take time to run depending on your setup.

v2:

I've updated this to a) pull data from the actual revenue source (Payments) instead of from invoices, and b) to display the most recent information first, making the more recent month's graph line be on top.

v3:

I've updated to incorporate refunds properly. If reversals occur, it wasn't backing out the negative revenue.