I had a look over this thread and having lived in many countries, I have some insights into how payroll differs between countries and how Tryton could support it.
The first insight I would emphasize is to break it down into logical pieces. Moreover, Tryton may not implement all those pieces. They may be developed by different people and at different speeds. These are some of the pieces of the puzzle, the client may use different tools for each step:
- employee contract management
- time reporting, vacation, sickness, etc
- calculation of the gross pay (convert days/hours to gross pay)
- calculation of the deductions (use gross pay to lookup tax and social security tables)
- booking the net pay and booking the deductions to G/L
- paying the deductions to authorities and insurance companies
- producing end-of-year reports by employee and by authority
The last three steps (booking to GL, paying bills, producing the annual reports) are fairly easy. You could almost do that using the existing tax code system. For some users who have a fixed salary for every employee and some freelancers, consultants and self-employed people this would be satisfactory. Their accountant will give them a spreadsheet, they photocopy the spreadsheet each month and use it as the payslip.
One important point to note is that when the amounts are booked to the GL, they may correspond to a previous year. E.g. the employee works some overtime on 31 December 2020 and the payment is made on 3 January 2021. For some reports the payment should appear in the 2020 tax return, for other reports the payment should appear in the 2021 tax return. Therefore, it is important to have some field, like the VAT tax point, that may not be the same as the payslip date or the payment date.
The idea of making this work like Invoice and Tax codes is very relevant. A tax code tree for payroll could be an interesting way to view payroll deductions (social security, tax, insurance, pension)