Work in the black or on the black?

Work in the black or on the black?
 

Why do people take the risk to work in the black or on the black?

I'm unaware of anyone who says 'work in the black' or 'work on the black'.
I think the set phrase in Spanish means to work illegally (or at a job that isn't official), but it could be something else.

If the 'illegal' component isn't inferred, we say:
take a job on the side
burn the midnight oil
work for pocket change
have a second/night job
moonlight
supplement one's income (on the side, on the down low)

I swear I heard sb using that expression. And yes it means to work illegally.
Working on the side rings a bell too.

I don't know if it's a British expression and, if it is, how it's used.

In Spanish trabajar en negro doesn't imply having other jobs like have a second job or moonlight

If it doesn't have the 'illegal' component, those are the phrases we use to describe working more than the norm. If the Spanish phrase means 'illegally working', we pretty much just say that (in AmE).

I think the common term is to work off the books.

'To work off the books' is self-employment, as I understand it, and can be illegal if taxes aren't withheld.

'To work off the clock' is time spent working for someone who doesn't pay you for that work. That's a crime (illegal).

If you're off the books (pagado en negro, that means you're being paid (under the table solapado) with no record, and nothing is reported. It's a common practice, and it's not legal. You'll see I right if you google the term.

The term paid and in the black means paid up and not owing anything. In the red means owing money.

We're saying the same thing. Getting paid under the table or off the books is illegal (because the government wants their cut, but there's no trail). A person who is working off the books could decide to pay taxes, and would have to file as self-employed to do so (and not divulge the source of the under-the-table money).

trabajar en negro in Spanish means that you are paid under the counter, and for the government you're unemployed. Without having a job on the side. You are in the unemployment list. What's the term in English? To work off the books?

Yes, 'to work off the books' or 'to get paid under the table' is a good match for the Spanish 'trabajar en negro'.

I searched for "work" within 4 words of "black" in the British National Corpus: most of the hits were talking about black workers, some were talking about black and white works of art, or the work of researchers on black holes. There were only three which are remotely relevant to this discussion: "work the black market" (borderline relevant), and "work in the black economy" (twice, and one of them had scare quotes around 'black economy').

The phrase which I think would be most applicable would be to "work cash-in-hand": i.e. being paid without receipts or bank records.

Thank you all, you do a big job in this forum, I m so glad there are people so efficient and altruist like you.