Receipts by Category report adjustments

We get a lot of questions about the amounts reported in the "Receipts by Category" report.  Sometimes the amounts in a particular category don't seem correct (e.g. a payment amount doesn't go into the category as expected), or an amount appears in "Uncategorized" and it's not clear why.  

The original article here is now included in the normal documentation (greatly expanded), so refer to that under Dynamic Interactive Report Screens / Transactions / Receipts by Category,