BACKGROUND One target of the Sustainable Development Goals is to achieve "universal health coverage, including financial risk protection, access to quality essential health-care services and access to safe, effective, quality and affordable essential medicines and vaccines for all". A fundamental concern of governments in striving for this goal is how to finance such a health system. This concern is very relevant for low-income countries. OBJECTIVES To provide an overview of the evidence from up-to-date systematic reviews about the effects of financial arrangements for health systems in low-income countries. Secondary objectives include identifying needs and priorities for future evaluations and systematic reviews on financial arrangements, and informing refinements in the framework for financial arrangements presented in the overview. METHODS We searched Health Systems Evidence in November 2010 and PDQ-Evidence up to 17 December 2016 for systematic reviews. We did not apply any date, language, or publication status limitations in the searches. We included well-conducted systematic reviews of studies that assessed the effects of financial arrangements on patient outcomes (health and health behaviours), the quality or utilisation of healthcare services, resource use, healthcare provider outcomes (such as sick leave), or social outcomes (such as poverty, employment, or financial burden of patients, e.g. out-of-pocket payment, catastrophic disease expenditure) and that were published after April 2005. We excluded reviews with limitations important enough to compromise the reliability of the findings. Two overview authors independently screened reviews, extracted data, and assessed the certainty of evidence using GRADE. We prepared SUPPORT Summaries for eligible reviews, including key messages, 'Summary of findings' tables (using GRADE to assess the certainty of the evidence), and assessments of the relevance of findings to low-income countries. MAIN RESULTS We identified 7272 reviews and included 15 in this overview, on: collection of funds (2 reviews), insurance schemes (1 review), purchasing of services (1 review), recipient incentives (6 reviews), and provider incentives (5 reviews). The reviews were published between 2008 and 2015; focused on 13 subcategories; and reported results from 276 studies: 115 (42%) randomised trials, 11 (4%) non-randomised trials, 23 (8%) controlled before-after studies, 51 (19%) interrupted time series, 9 (3%) repeated measures, and 67 (24%) other non-randomised studies. Forty-three per cent (119/276) of the studies included in the reviews took place in low- and middle-income countries. Collection of funds: the effects of changes in user fees on utilisation and equity are uncertain (very low-certainty evidence). It is also uncertain whether aid delivered under the Paris Principles (ownership, alignment, harmonisation, managing for results, and mutual accountability) improves health outcomes compared to aid delivered without conforming to those principles (very low-certainty evidence). Insurance schemes: community-based health insurance may increase service utilisation (low-certainty evidence), but the effects on health outcomes are uncertain (very low-certainty evidence). It is uncertain whether social health insurance improves utilisation of health services or health outcomes (very low-certainty evidence). Purchasing of services: it is uncertain whether increasing salaries of public sector healthcare workers improves the quantity or quality of their work (very low-certainty evidence). Recipient incentives: recipient incentives may improve adherence to long-term treatments (low-certainty evidence), but it is uncertain whether they improve patient outcomes. One-time recipient incentives probably improve patient return for start or continuation of treatment (moderate-certainty evidence) and may improve return for tuberculosis test readings (low-certainty evidence). However, incentives may not improve completion of tuberculosis prophylaxis, and it is uncertain whether they improve completion of treatment for active tuberculosis. Conditional cash transfer programmes probably lead to an increase in service utilisation (moderate-certainty evidence), but their effects on health outcomes are uncertain. Vouchers may improve health service utilisation (low-certainty evidence), but the effects on health outcomes are uncertain (very low-certainty evidence). Introducing a restrictive cap may decrease use of medicines for symptomatic conditions and overall use of medicines, may decrease insurers' expenditures on medicines (low-certainty evidence), and has uncertain effects on emergency department use, hospitalisations, and use of outpatient care (very low-certainty evidence). Reference pricing, maximum pricing, and index pricing for drugs have mixed effects on drug expenditures by patients and insurers as well as the use of brand and generic drugs. Provider incentives: the effects of provider incentives are uncertain (very low-certainty evidence), including: the effects of provider incentives on the quality of care provided by primary care physicians or outpatient referrals from primary to secondary care, incentives for recruiting and retaining health professionals to serve in remote areas, and the effects of pay-for-performance on provider performance, the utilisation of services, patient outcomes, or resource use in low-income countries. AUTHORS' CONCLUSIONS Research based on sound systematic review methods has evaluated numerous financial arrangements relevant to low-income countries, targeting different levels of the health systems and assessing diverse outcomes. However, included reviews rarely reported social outcomes, resource use, equity impacts, or undesirable effects. We also identified gaps in primary research because of uncertainty about applicability of the evidence to low-income countries. Financial arrangements for which the effects are uncertain include external funding (aid), caps and co-payments, pay-for-performance, and provider incentives. Further studies evaluating the effects of these arrangements are needed in low-income countries. Systematic reviews should include all outcomes that are relevant to decision-makers and to people affected by changes in financial arrangements.