Hi there: A GST payment is not an expense. It cannot be put to an expense account and end up reducing revenue.
Did you not have opening balances for this company that you started entries for at Sept. 1/06? How did you know what the opening bank balance was or the opening Retained Earnings, or the Fixed Asset values etc. were? You say there was no account payable set up for the amount of the payment. If you have a trial balance from Aug. 31, 2006, to start out the company with, there should have been GST Charged on Sales and GST Paid on Purchases accounts with balances. (Not to mention all the other Balance Sheet balances that should have been brought forward.)
However, you say the amount paid was for 2004/05. Do you have any paperwork from the GST people to document what that payment was for? And just out of curiosity, what was happening about GST owing from 2005/06? You say that the GST accounts are up to date -- but they only have what you have been entering. Flip through your cheques written and see if somewhere further along there was a payment for the 2005/06 year.
You do have a bit of a dilemma because you don't know if the full amount of Sales, including the GST Charged on Sales, was reported as Revenue. If it was, and the GST Charged wasn't split out the way it should have been, then revenue for the previous years would have been overstated. However, that doesn't help you much since you likely can't find out what happened. I would ask the owners if they remember what happened and how the GST was being done. The other thing you can do is to phone the GST people and ask for copies of all prior returns and assessment notices. If you can get those it would be a good starting point.
In order to take care of recording the payment of GST for 2004/05, my thought would be to post the Credit to Bank and the Debit to Retained Earnings, Prior Year. But that would only be correct if your Retained Earnings balance when you entered your opening balances didn't agree and needed to be changed to reflect the GST Payment. Were you the one that posted such a problem a few days ago -- that the opening balances were changing the Retained Earnings and that it didn't agree once you had put all the amounts from the trial balance in? If not, disregard that question.
Anyway, do a little investigating before altering a prior year's Retained Earnings. Rita Deering