Slip Date Filer not Working

I'm relatively new to TS in a law office.  Every time I try to limit the bills to be generated, by slip transaction date (i.e. for slips for 1 month only) I still get clients' bills showing up that are months' old and have been paid.  I also use the Professional filter which works fine. 

Not every client gets billed every month; it depends upon the activity in each case for any given month.  So, I end up going through the whole list of clients and just deleting those I don't want to include in the run.  Very time-consuming.  How can I get the date filter to work?  Is there another way to limit the bills to be generated?

Thanks