This study examined the associations between socioeconomic factors (SEF), readmission, and mortality in patients with incident heart failure (HF) with reduced ejection fraction (HFrEF) in a tax-financed universal health care system.Lack of health insurance is considered a key factor in health inequality, leading to poor clinical outcomes. However, data are sparse for the association between SEF and clinical outcomes among patients with HF in countries with tax-financed health care systems.A nationwide population-based cohort study of 17,122 patients with incident HFrEF was carried out. Associations were assessed between individual-level SEF (cohabitation status, education, and income) and all-cause, HF, and non-HF readmission and mortality within 1 to 30, 31 to 90, and 91 to 365 days, as well as hospital bed days within 1 year after HF diagnosis.Low income was associated with a higher risk of all-cause readmission (adjusted hazard ratio [HR]: 1.24; 95% confidence interval [CI]: 1.08 to 1.43) and non-HF readmission (HR: 1.36; 95% CI: 1.17 to 1.58) within days 31 to 90 as well as with a higher risk of all-cause (HR: 1.27; 95% CI: 1.14 to 1.41), HF (HR: 1.26; 95% CI: 1.02 to 1.55) and non-HF readmission (HR: 1.25; 95% CI: 1.12 to 1.39) within days 91 to 365. Low-income patients also had a higher use of hospital bed days and risk of mortality during follow-up.In a tax-financed universal health care system, low income was associated with a higher risk of all-cause and non-HF readmission within 1 to 12 months after HF diagnosis and with HF readmission within 3 to 12 months among patients with incident HFrEF. Low-income patients also had a higher number of hospital bed days and a higher rate of mortality during follow-up.