There’s a good chance AmEx will not reverse (claw back) the airline fee credit thus it will show as “used” until January 1st.

Presumably “fee charge post back to my account” refers to a credit to your credit card by United. If AmEx recognized that credit as for a charge that AmEx had previously posted an airline fee credit, AmEx might possibly reverse (claw back) the airline fee credit in which case it might show as a new charge, not listed as “airline fee credit reversal”, to your account.

I’ve (unintentionally of course ) done something similar the past 2-3 years which resulted in my getting the AmEx Aspire Hilton Resort annual credit. On January 1st, booked a Hilton ski resort for March which required a deposit (coincidentally more than the maximum credit of $250 ). Deposit posted in a day or 2, AmEx Hilton Resort credit posted a few days later. Unfortunately my plans subsequently changed and I cancelled the reservation a day or 2 after the Hilton Resort credit posted, Hilton refunded the deposit 7-10 days later, AmEx never reversed the credit. (At the times involved I’ve put other charges on the card which is used only 2-3 times a year for Hilton stays, sometimes plan a retention offer for the same timeframe for that reason, so that my statement does not show a credit balance which might be more attention getting.)

Screenshots below show the appearance of an AmEx (CLEAR fee) credit claw back. New Biz Plat account September 2022. Most of the transactions are self-evident including my notations. I paid my CLEAR membership fee in Oct 2022 and AmEx quickly credited it. In May 2023 I added my niece, CLEAR charged a prorated (to my renewal date in October) amount of their Family ($60) rate, AmEx quickly credited it (maximum annual CLEAR credit is $189). While discussing with CLEAR adding my niece, I learned that CLEAR Military rate ($99) is lower than UA elite rate ($109) and a lovely CLEAR phone agent told me once I show my Military credentials at a CLEAR lane, CLEAR would reimburse me $20 for my past 2 years CLEAR fees paid and charge me $99 going forward.

End of May I showed my Military ID at a CLEAR lane. (Took 3 or 4 different agents and finding a CLEAR manager for CLEAR to know what to do but that’s a horse of an entirely different color .) Called CLEAR again, told them Military status added, CLEAR refunded $20 to my credit card on Jun 2 as below. The next transaction “CLEAR NEW YORK $20.00” is a charge to the credit card by AmEx (I confirmed that with both CLEAR and AmEx) to reverse (claw back) $20.00 of the previously issued CLEAR fee credits.

So, if you don’t see a corresponding charge for the amount of your previous Airline Fee credit, probably relatively shortly after receiving the credit from United, you’re probably in the clear (no pun intended of course ). Since you received the (annual) credit, it will show as “used” for the rest of the year. Although you didn’t end up “using” it for the cancelled trip, from AmEx’s point of view it was “used”.

I hope that’s clear (as mud … of course no pun intended again ).

(Please pardon my verbosity, I rarely pass up an opportunity to explain in 3 pages what could easily be explained in 3 sentences !)