How to convert sales tax from accrual basis to cash basis on QuickBooks?
There is no easy way. You can print the open invoices report as of the end of 2009. Print the same report at the end of January and look at those invoices that are due for more than 30 days. The difference should give you the sales you already paid the sales tax on and that is added again to the January sales and sales tax. There is no automatic way to make QuickBooks figure out the double-reporting because of the switch from accrual to cash basis.
