@Apples521 

"It's also entirely possible, even likely that the payments were not actually even received in 2022/2023, but just recorded as such in QB."

If the payments were received in 22/23, then this is presumably income because there's no open receivable. If both the 22/23 payments and 25 payments were retention, shouldn't it be relatively easy to determine whether the retention amount should have been +/- $4,500 or $9,000 based on the job?

"Since the bank currently balances and assuming there's no other place for those 2022/2023 payments to go, what do I do with this payment received in Jan 2025?"

If the payments weren't received in 22/23 but were recorded as received in QB, then posting it to retained earnings (RE) makes sense (with good notes to explain).  The CPA will surely see the $4,500 change in RE and can determine the most appropriate adjusting entry from there.  The other option is to post it to Ask My Accountant (expense).  That's may or may not be an option depending on how you want the P&L to look.  Either way, the CPA will ultimately have to make the adjusting entry.  Just my $.02.