What have you actually posted with the wrong date?  Now I'm guessing at what the problem is, but when you reconcile the VAT return you have the option to post the journals to the VAT accounts.  Annoyingly, Sage uses the current program date rather than the period you want to post into, even though the VAT transfer box gives the correct date to use. If that's what's happened, just make a note of the journal that's been posted and post a journal with the exact same date but reversing the debits and credits. That takes it out of the "wrong" period. Then post the original journal again, but with the correct 31st Dec date.  

If this was the problem, it can be avoided next time by going to Settings, then Change Program Date to the period end date you want to use (in this case 31/12/22).