Many people then find that they have been undertaxed on their total income and they need to pay more in to Sars, an independent broker from Consult at Momentum, says the default tax deduction as prescribed by the SA Revenue Service (Sars) on joint income affects certain pensioners’ monthly cash flow, but ultimately they do not pay more tax for the year. Rather, all income appears on one’s tax assessment for the year and one is taxed accordingly.