As someone who grew up with a mother who is a personal tax-account this is the first thing I thought of too to express this in English. I've never heard it expressed as asking if a person or business is liquid, but rather solvent.
I would like to know if the French liquide can mean the same thing?
So, there is another question similar to this that does not have a discussion option, so I figured I'd ask it here:
Write “cash” in French
I wrote "le liquide" and it is not accepted (it only accepts "la monnaie"). Does "liquide" REALLY mean cash, or is it slang that is only accepted in certain phrases?