This paper investigates the causal impact of contract tailoring in the FinTech lending sector using a randomised field experiment and extensive administrative data from a leading digital lender in Indonesia. The study finds that synchronising loan due dates with income cycles (payday alignment) reduces delinquency by up to 29.1% in the experiment and 15.7% in broader administrative records. These benefits are most pronounced among liquidity-constrained groups, such as young and low-income borrowers. Additionally, the research demonstrates that tailored repayment timing leads to improved future credit access for borrowers and accelerated cash flows for lenders.