> It was all for free.

Awesome. You used the term "under the table", which I've always understood to mean a cash transaction that won't be reported in tax filings.

'Under the table' means 'out of sight'. It is used to indicate money changing hands but that's not the only use.

Every single time I've heard "under the table" it means "without documentation" and is used in the sense of not paying taxes.

I've never heard anyone use the phrase "under the table" unless there was money being exchanged for services without going through the proper channels. Your understanding was spot on. This was a bad use of a very old phrase.

> This was a bad use of a very old phrase.

This seems like a bit of a stretch. Just because you haven't heard a term used in different contexts doesn't mean it's invalid. On review of the same text I may have rephrased it, but while imperfect, it's still understandable in the context.