The HUD Payment Integrity and Accountability Act of 2026 requires the Department of Housing and Urban Development to complete a comprehensive assessment of improper payments in its rental assistance programs by December 1, 2027. The assessment must evaluate both project-based assistance, which provides subsidies to specific housing properties, and tenant-based assistance, which helps low-income renters pay for housing of their choice. The bill also establishes fraud detection requirements that mandate HUD notify its Inspector General within 60 days whenever it identifies unusual spikes in assistance payments or the number of landlords participating in a geographic area, such as increases exceeding 100 percent in a single year. The HUD Inspector General is tasked with conducting audits of high-risk programs and geographic areas, submitting a separate fraud risk assessment focusing on the roughly $50 billion in annual rental assistance spending, and pre-certifying that HUD's assessment methodology is statistically sound before the December 2027 deadline.