I find the easiest way to wade through all of the payment issues is to use windows live calendar and a spreadsheet (I use Microsoft Office.) I post my shops to a separate calendar overlay in Windows Live Calendar (This is a tab in windows live mail.) You can then click on reminders and it will automatically send you an email to remind you when the shop is scheduled. You set the time to for the reminder email as to your own preference. I usually set it at 1 day in advance.
After the shop is complete, I have a spreadsheet set up that I enter the shop information into. I have a tab with all of the MSCs I work for payment promises and actual payment experiences. I then estimate a date from the payment experience or the payment promise from the MSC and enter it in the spreadsheet.
I then go back to Windows live calendar and copy and paste the completed assignment to a different overlay I labeled pay dates. Again I set an email alert.
Each time I get paid, I add the actual pay date to the spreadsheet and check the payment amount for each shop and reimbursement. If I get paid early, I update my experience tab and reflect the current time frame. I also got the Live calendar and delete the payment due date. This way I only get alerted If a payment is not made as promised or experienced in the past.
It took me an hour to input 147 shops into the spreadsheet when i started it. The calendar took less time because most of the info was copy and paste and then edit.
Now with just a couple of extra key strokes, I have an automatic payment forecast that works pretty well to estimate for cash flow. It also reminds me when my shops are due and when to follow up on late pays or short payments. I also use the spreadsheet to record confirmation numbers from report submittals and any bonus or increased payment info on the shops. I record who offered the bonus, how much and how I was offered the bonus or increased reimbursement. Having the who, why and when for payment issues makes it very easy to resolve.