Equity in utilization and resource distribution is an essential intermediate objective of health financing policy . The achievement of this objective leads to health gains and financial risk protection, especially for those in need. Since 2000, the WHO has drawn attention to ensure equitable (or fair) financing for health care, highlighting that health systems are not just about improving health status. However, also improving fairness through health system financing and delivery has a broader social value . In the 2010 World Health Report, the fair financial contribution was considered to be the main criterion for achieving universal health coverage. .
Generally, different methods have been used to finance health systems, including tax-based insurance, social insurance, private insurance, and Out-of-Pocket (OOP) payment . From the viewpoint of both risk protection and equity, OOP payments is considered to be the worst possible form of health financing [5, 6]. Evidence shows that the high share of OOP payments for health services is a sign of inadequate social health coverage and can lead to economic hardship, particularly in low-and middle-income countries [7, 8]. OOP imposes the most significant burden on the poor and carries a high risk of falling households into poverty by imposing Catastrophic Health Expenditure (CHE) . To this end, WHO has more than ever emphasized the CHE and the Fair Financial Contribution Index (FFCI) as equity indicators for household financial contributions to health systems [10, 11] and recommended the universal health coverage strategy with the aim of ensuring that all people have access to the required health services without any financial difficulties at the time of receiving services.
In Iran, given the requirements of the National Five-Year Development Plans to address high OOP rates, i.e., 52.1% of total health expenditure , the increased contribution of the government in providing the funds for public health expenses and appropriate allocation of public resources in the health sector are of great importance. Accordingly, in May 2014, the Ministry of Health and Medical Education (MoHME) of Iran implemented a comprehensive health system transformation package called the Health Transformation Plan (HTP) . The reduction in the percentage of OOP payments and the reduction in the percentage of households facing CHE were identified as top priorities in HTP content.
Even though various indices such as the Kakwani index, Gini coefficient, CHE, and the impoverishment index  can be assessed for the performance of the health system, the WHO emphasizes the FFCI as an essential measure [11, 15]. Fairness in healthcare financing is assessed by the level of inequality in the payment of health care between households of unequal Capacity to Pay (CtP) .
Overall, equitable financing is a crucial objective of healthcare systems and healthcare financial risk protection, recommended to be measured on a continuous and periodic basis every 2–5 years [5, 17].
The present study aims to how the HTP achieved its objectives in terms of fair financial protection by assessing FFCI in various households of urban and rural areas before (2008–2013) and after (2014–2018) the implementation of the HTP.