How will tax be calculated after I leave my job?

Your tax will be calculated based on the amount earned to date of the tax year. Your PAYE has already been paid over for the months worked. Your final month worked will most likely include a larger income amount and this will be taxed as per the SARS tables. When you file your final tax return for the 2014 tax year then your tax payable will be calculated for the year and you most likely will receive a refund. However I cannot tell you how much the refund will be just yet nor the tax rate of the final month without knowing the amount earned.