I have been thinking Saturday, Saturday, Saturday. Well, that is wrong.
So then you figure it must be Monday, right?
Nope. The Dr. MLK, Jr. holiday is Monday!!
So we have until Tuesday, January 18th, to use that card and make those quarterly tax payments. Sometimes you just gotta love that sweet calendar. 
Current Vanilla GC status:
Metabank works with ACI and PayUSAtax, but not Pay1040.
Sutton works with ACI and Pay1040, but not PayUSAtax.
I’m still waiting for the IRS to refund my 2020 overpayment (I only received a partial refund). I even called, promises were made but not yet fulfilled. And now the wife got the notice telling her how much she received in Advance CTC payments, even though she never received the payments (I opted myself out, but, unfortunately, didn’t ask her to do the same). I’m as unhappy with the IRS as I’ve ever been 
.
Recent reporting by the USA mainstream media is saying the IRS has been hit VERY hard by the pandemic. They are remarkably far behind with their processing of just about everything.
Patience will win the prize. But I cannot tell you when. People who overpaid to facilitate I bonds purchase I still think were smart and did the right thing. But for others, including perhaps even those seeking to harvest extra CC rewards:
Given the pandemic, this is not a good time to overpay your taxes. Wait until the pandemic is behind us.
I get that some services are affected more than others by the pandemic but that’s also becoming an all too easy get-out-of-jail card for covering ineptitude.
Granted Congress piled on unnecessary hand outs like the advance payment of Child Tax Credits but still.
That said, you’re correct that you’d be remiss to overpay due to their processing times currently. Especially at the current inflation rate. If they give you back your money a year later, it’s effectively worth 5+% less due to inflation.
That was another bonehead move by the IRS/Congress to not make it opt-in for those who needed the cash advance rather than an unadvertized cumbersome opt-out that was individual regardless of prior filing status. I had opted out, thought that it would cover our household since we always file jointly, but did not make my husband do the same until after we received the first check. Now it’ll make our return more complex for giving us money we’ll end up returning to them since we always owe.
My 2020 return was filed in March. It was put on hold due to a technicality. They never bothered to contact me about this hold, and I waited patiently for them to process it, believing the news reports of them being severely backed up. But in November, I finally called to see what was up, was told about the hold, they quickly cleared it (without my even asking, let alone needing to do anything to resolve it), and I had my refund less than 2 weeks later.
At least I got interest for the delay.
That was before we knew how good I-bonds would be, so I did it for the rewards, but I won’t mind the interest… assuming they’ll pay interest on overpayment.
When I called in November, I was told my money was held back in error and would be refunded by check (even though my actual refund was by ACH) in 4 weeks. I just hope it won’t be sent to the same place as my wife’s Advance CTC checks that we never received…
I filed in October and nothing, not even a status, on the IRS web site. Hope they will pay out by April and receive six months of 7.12% interest, but it may not.
The way things appear headed with this inflation, the next six months after the reset might be even higher than 7.12%.
That is true. The good news about ID.me is that it’s also used by the SSA (to access My Social Security) and apparently the DMV (at least in CA).
The problem with the Account Transcript is that it didn’t tell me why my money was held up, only that it hasn’t been refunded like promised. It also didn’t tell me anything before my tax return was processed (I’m calling it the great tax return limbo of 2021).
Really? That’s good news? /pedantic analogy mode B̶i̶d̶e̶n̶e̶d̶ broken. 
Mine as well. It showed the return was received, and what the numbers were and the refund amount would be, but there was no indication that there was any issue holding up processing the refund.
Ah, you’re right, it’s all very, very bad.
I finally got the rest of my 2020 refund. With interest, though it appears to only be about 3%.
Just made my first 2022 estimated tax payment using Pay1040 and excess capacity on one of my cards (PenFed). There was no drama. It all went smoothly. The profit is very minimal. But since I had the capacity, because PenFed will make my reward available within a few days, and for the sake of ease and convenience, I went forward with the payment. I love that PenFed issues rewards so quickly. It’s nice. And this way I won’t have to actually pay my tax bill until first of June.
State tax. It’s a different story . . . at least where I live. Thinking . . . . .
ETA
Well, well . . . .
As things have turned out the above is completely wrong. I have no clue what is going on:
This is not my first “pay the IRS with a credit card” rodeo. I have paid that way many times. Never had this happen:
While the service fee is showing (correctly) as a pending charge, my actual (far larger) payment amount to the IRS is nowhere to be seen when I log in to my PenFed account. I always check stuff like that.
Called them
The rep could see the actual IRS payment and told me it is pending, which would be correct. But they do not know why I cannot see the same thing when I log into my account here at home!!
They told me to wait until tomorrow. Very unsatisfactory customer service on an important payment.
PenFed very recently “upgraded” their credit card GUI, making it much fancier but certainly no more useful. I’m hoping they have some sort of glitch.
If it ain’t broke, don’t fix it. They fixed it all right. 
I cant say I’ve ever heard someone be upset they dont see a pending notation for a charge. Most people get excited in the hopes that it means the charge will never post to the card.
I’ll just note that you can get a new Discover Card and net a hair over 1% on these payments for the next year, or a 1% debit card (like Discover Bank) and net a hair under 1%. Still not lucrative, but it’s better than a kick in the teeth…
nothing for me yet 
most recent transactions on irs.gov:
Transcript
FORM NUMBER: 1040 TAX PERIOD: Dec. 31, 2021
766 Credit to your account 12-20-2021 -$291.00 (child tax credits)
846 Refund issued 12-15-2021 $291.00
290 Additional tax assessed ?? 12-20-2021 $0.00
It’s a payment to the IRS. The deadline for this payment is 15 April . . . tomorrow.
I have made many payments this way to the IRS across all three services. Without exception I always see two pending charges to my card immediately, one for the service fee and the other being the amount going to the IRS . . . but not this time.
I hope it is just that PenFed is FUBAR. That would be good. I hope it is not that they are considering denial of my charge. This payment to the IRS must be made timely. I do not have room to tolerate any foolishness from PenFed. And when I inquired I was unable to obtain a straight answer. That did not, and does not, inspire confidence.
I have credit out the wazoo. Choosing PenFed for this critical IRS charge was a mistake I will not repeat.
You gotta be careful with what you click on. I believe the transcripts for 2020 and 2021 are separate and different. If you’re waiting for something from 2020, the “TAX PERIOD” should say “Dec 31, 2020”.
Point being that the payment to the IRS is a separate transaction from the charge being made to the credit card. Myself, I couldnt care less if the third-party company I use debits my payment method or not, I only care that they send funds to the payee. A pending charge on my credit card is in indication of the former, not the latter.
Yes, I’m currently sitting on just such a payment from nearly 5 years ago, where the payment was made but my card was never charged.