A money market account is a different story. That's fine, that's where my quarterly payments live. When the OP said "invest" I assumed they meant "put that shit in equities and let it ride".
There's numerous equities (safe and not) to invest in; usually the higher the risk the better the payout. This is really the only choice you get to try and make is how much can I try and save up?
My opinion, and that's all it is, is that the moment the money comes in, some percentage of it is no longer my money. It's the government's, whether I like it or not. I don't play games with other people's money. Making a little safe interest on the quarterly float is fine, but I'm not going to risk losing it, because I don't want to incur their wrath, and I very much don't like being in debt to an entity who can force my 1099 payers to withhold on my behalf.
Maybe an unpopular opinion, but I'd rather be safe and in the IRS' good graces than try to earn a margin on their money net of their penalties and interest.
