> That isn't a question I have ever needed to ask, nor do I expect to, but if I do, it would be answerable with a single query over a single-entry transaction list.

How would you pick out just the transactions that were to your ISP? Unless you want to manually review the transaction log, you need something consistent you can refer to in your query: like an account name (or a transaction description, but that feels easier to accidentally be inconsistent with).