I love this question. I get a peek at what others are doing.
I started with the starter Excel spreadsheet here. It morphed into a workbook. The first worksheet is a summary of all the MSCs I worked for with links from the MSC worksheets. The live cells are the totals of the mileage (*2), the amount owed and the amount paid. This sheet goes to Tax Dude. I can also see who owes me what.
The following worksheets are the individual MSCs. These have the details of the shops that I do for them. At the bottom of the sheet, miles and money are totaled and linked to the summary sheet.
The last worksheet the a list of the MSCs from the bottom of this page. This sheet has my log in information if I am registered with them.
I use Google Calendar to know what I'm doing day to day.
"I told myself to quit you; but I don't listen to drunks." -Chris Stapleton