The SMOOTH Payments Act would change eligibility rules for federal health insurance premium tax credits by requiring that insurance companies offer at least one health plan with monthly cost-sharing payment options. Under this bill, individuals would only be eligible for the tax credit if their insurer offers a plan allowing them to pay zero out-of-pocket costs at the time they receive medical services and instead pay their cost-sharing obligations in monthly installments, similar to how prescription drug costs are handled under Medicare. The legislation would exclude catastrophic health plans and any plans offered by insurers that don't provide this monthly payment option from the tax credit program. The changes would take effect for tax years beginning after December 31, 2026. This bill aims to make healthcare costs more manageable for consumers by spreading out-of-pocket expenses across the year rather than requiring immediate payment at the point of care.