I am working on an Australian payroll module for Odoo and due to the complicated way our tax system works I need to be able to call a method in the employee object and pass it some parameters (such as date to and the taxable income for the payment period) which would then look up the relevant tax table and return the tax to be deducted from the employee's pay.

I have a method in hr.employee calculate_paygw(self, cr, uid, ids, date, taxin, context=None) and attempt to call it within a salary rule. The problem is that it is never called and I get an error - wrong python code defined for salary rule.

Is it possible to call a method on an object within a salary rule? If so, how do I do it?