Do you check every bill and keep receipts?

We do - or rather, I do.  I keep all of our charge receipts and medical payment receipts to check against bills and insurance claim forms.  We charge almost everything for convenience so this covers most of our spending.  I do track the cash spending but it is a small percentage of our outflow.

Rarely do I find a problem, but when I do usually it is in the medical expense area and always in our favor.  Today I wanted to pay the bill for some of hubby's medical expenses.  He had mistakenly paid a copay for his most recent physical and the clinic had credited that as an insurance overpayment.  It was "only" $20 but a phone call easily got it credited to what we owed and we saved $20. 

I don't enjoy doing this at all but sometimes it pays off.  Have you found errors in billing or credit card statements recently?