WCB payable should always have a cr balance unless you have overpaid your WCB remittance or you are not calculating the correct amount of WCB payable when you pay your employees. If your balance sheet is showing a minus figure it has a dr balance.
To check, go into each employee's setup and ensure that you are calculating the correct percentage each payroll.
If the calculations are correct pull out your past WCB remittance(s) and find the one where you made an overpayment.
If your overpayment is happened in the current fiscal year and you will be making another remittance in this fiscal year you can fix it by underpaying the next remittance. If you will not be making another remittance this fiscal year you can correct it by making a general journal entry to cr WCB payable and dr WCB expense.
If the error is in a previous fiscal year talk to your accountant about whether the amount is significant and a previous year adjusting entry - and perhaps amended tax return - needs to be prepared.
As far as your allowance for doubtful accounts is concerned, many businesses know from experience that they will not collect all their A/R although they cannot specifically identify which ones will not be collected. In this case they will make an allowance for these accounts as an offset to their A/R on the balance sheet. The entry is a dr to bad debts and a cr to allowance for doubtful accounts. As specific bad debts are identified the A/R is written off and the allowance reduced. To follow this procedure and have it accepted by the CRA you need a history which shows you have needed to write off uncollectible accounts in the past.
If you cannot show this kind of history you will need a good reason to convince the CRA (and probably your accountant) why you are expensing bad debts to this allowance.
Your payroll advances account should only have a figure in it (and it should be a dr) if you have made advances to employees that have not yet been recovered through payroll.
