@Involver wrote:Is there anything prevent somebody from overpaying their taxes by, oh, $20,000?
Per IRS.gov:
"If you overpaid, IRS will refund it after the return is processed, excepting offsets or debt on your account."
Edited for brevity to allow for continuance of discussion.
Bad value. Bad idea. Just bad. First off, you will get hit with a fee to pay your taxes with a credit card, so your profit margins will be slim and in some cases the fee will eat up the rewards. Second, you are giving the government money and then waiting for a refund. What if the government decides they don't agree you are entitled to your full refund? I pay taxes with my credit card for convenience and I have to be very careful which card I use, because some cards will result in a loss. Can it be worth it to meet initial spend? Sure if you need to make the spend anyway. Beyond that then no and clearly overpaying is a losing proposition
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Oh when I file this year I will be paying approx 1k I will owe the gov't by CC to meet spend.. So 3% or $30 is wel worth it for me, also rewards is 1% back so make that $20... I am not overpaying them, it is completly legit imo as you are paying a fee.. Overpaying I don't see being benefical as the 3% fee on paying taxes.. My case to meet min spend of what i TRUELY owe, I see no ethical issue with it all all.. What I do see an ethical issue with is I will never see my SS from the gov't when I retire.. So ya they have stoen several hundred thousand from me in the biggest pyrmaid scheme in the history of the world
... Is that ethical? Granted we are talking taxes and cc companies here.
If it has to do with rewards its "unethical" 
@Involver wrote:The way I look at it.
If you're trying to meet, say, $3k initial spend, and you don't have heavy regular spend every month.
You pay $56.10 for the convenience of getting it over with.
You can pay with a 2% card and make 0.13% on paying your taxes. It's not a lot of money, but it's free money on top of something you'd be doing anyways.
That is a slim margin and it is true you would make that minimal profit. What you should also consider is that you are spending extra money in the meantime (in the way of fees) that you will not recoup until you redeem your rewards, which could be much later down the road. I would only recommend paying taxes this way if its for convenience sake or if there is just no other way to make the initial spend. Otherwise I think you will earn more reward value from meeting initial spend via other means.