Additional to the OP's request, this feature should be based on payment.  My customer's should not be receiving a payment reminder if they've already paid.  Quickbooks seems to be behind the times.  Not only were we forced to the online version, but it's extremely lacking.  Many of the feature requests are not only present in other book keeping software, but were present within the desktop version; which I can only assume we were forced from out of greed, quadruple the money yearly for 25% of the features.