And these agencies have been doing it for decades. So what’s the big deal.
Federal Agencies
• IRS (Internal Revenue Service, Treasury): Tax returns, income, banking, family data; central for rebates/stimulus verification.
• SSA (Social Security Administration): Earnings, benefits, SSNs; heavy data matching for programs.
• Treasury / Bureau of the Fiscal Service: Processes payments, rebates, stimulus; financial transaction oversight via FinCEN.
• HHS / CMS (Health & Human Services / Medicare & Medicaid): Health, medical, eligibility records for benefits.
• Department of Education: Student aid, loans, income verification.
• DHS / FBI / DOJ: Immigration, law enforcement, security via data matching and purchases from brokers.
• Others (e.g., OPM for background checks, VA for veterans).
These often use computer matching agreements across agencies for fraud/waste detection and rebate eligibility. 
Private Entities
• Credit Bureaus: Equifax, Experian, TransUnion — credit histories, financial behavior.
• Data Brokers / Information Resellers: Aggregate and sell public purchased data (addresses, purchases, interests, etc.) to government or businesses.
• MIB, Inc.: Medical conditions for insurance underwriting.
• Medical Record Retrieval Firms (e.g., CIOX Health, others): Pull health records for insurers, law firms, claims.
• Banks / Financial Institutions: Report via GLBA; share with regulators like CFPB.