1 SUMMARY 2 3 It is increasingly recognized that financial incentives can motivate behavior change and improve outcomes 4 along the HIV care continuum. Under the right circumstances, financial incentives can increase the demand for 5 HIV testing, change short-term sexual behavior, enhance linkage to care after HIV diagnosis, and promote 6 antiretroviral therapy (ART) adherence. However, despite a proliferation of cash transfer studies for HIV 7 prevention in Sub-Saharan Africa, there are few studies of cash transfers’ effect on adherence and/or retention 8 among people living with HIV infection (PLHIV) in Sub-Saharan Africa. 9 The proposed research will advance global knowledge about cash transfers for PLHIV and calibrate the 10 minimum cash transfer size, best delivery strategy, and effect on viral suppression at 12 months. We will build 11 on preliminary data from a study we conducted demonstrating that short-term cash transfers can improve ART 12 adherence and retention in care among food insecure PLHIV in Tanzania. We will now leverage our 13 established research program in Tanzania to optimize our short-term (6 months) cash transfer intervention for 14 retention and ART adherence in order to maximize effectiveness and facilitate scale-up. The overall goal of our 15 intervention is to briefly intervene during a window of opportunity to support the development of good 16 adherence habits, protect individual and household welfare during the vulnerable time near treatment initiation, 17 and develop a cash transfer system that could be implemented in the real world. We have designed an efficient 18 research plan with two linked studies to fine-tune the intervention and its delivery and confirm its effectiveness 19 on retention in care and viral suppression among recent ART initiates. We will first determine whether a 20 smaller cash transfer can achieve similar benefits on retention in care and viral suppression (Aim 1). After 21 selecting an optimal cash transfer size, we will implement a cluster-randomized trial in 32 facilities to: 1) 22 evaluate the cash transfer intervention for effectiveness on 12-month viral suppression (Aim 2); and 2) conduct 23 a mixed methods process evaluation using an implementation science framework to understand facility-level 24 successes and challenges as they implement the intervention through the mHealth system (Aim 3). 25 At the conclusion of the project, we will have validated an efficient and scalable model of the intervention and 26 its effectiveness, consistent with an implementation science approach to close the gap between evidence and 27 practice in real-world contexts. This timely information will be widely applicable to the spectrum of cash transfer 28 programs currently being designed, implemented, or under consideration to improve the health of PLHIV.