I sometimes have trouble keeping track of the due dates of the monthly bills. To help manage this, as the bills come in the mail I first place them in an expanding file, organized by their due dates. Then, on a monthly calendar, I write the bills in according to their due dates, or the date they need to be mailed if it's not a bill that's paid online. I also enter this date on an "event reminder calendar" (from a Hallmark card computer program), that pops up on my computer each morning, so I know what's due to be paid or mailed that day. That way, nothing is ever late because I forgot!