If all purchases Sales Tax are subject to the same duty rate, the dues allowance itself is leveled with higher income people paying extended bite as they consume more. While the assessment on spending as a percentage of gross income may be regressive, the effective excise rates can be progressive on consumption due to exemptions or rebates. If a sales capitation is to be related to income, then the unspent income can be treated as tax-deferred (spending savings at a later count in time), at which bit it is taxed. Sales taxes often exclude items or provide rebates in an effort to compose progressive effects. In abounding locations, "necessary" items such as non-prepared food, clothing, or prescription drugs are exempt from sales bite to alleviate the burden on the poor.