in the insert page, add the Taxable checkbox. set the checked value to 1.
in the server behaviors panel, double click the Insert record server behavior. bind the taxable database column to the taxable checkbox.
For the update page, follow the same steps, except you will be double clicking the Update record server behavior.
to make the checkbox show the state that is already set in the database, select the checkbox in design view.
in the property inspector click the dynamic button. Click the lightning bolt next to Check If and select the Taxable column from the products recordset. Enter "1" (without quotes) in the Equal To box.