No, MFA is not enforced everywhere in US enterprises as of January 2026.

There is no universal federal law or regulation mandating MFA across all private-sector US companies or all enterprise systems. Adoption is widespread and strongly recommended (or required in specific cases), but it's not blanket-enforced nationwide.

Key points on the current landscape:

• Strong recommendations and best practices — CISA, NIST, and many cybersecurity experts push hard for enterprise-wide MFA. CISA's "Secure Our World" campaign urges businesses to require MFA "wherever possible," especially for admins, remote access, email, and privileged accounts. It's seen as blocking ~99% of common account compromise attacks.
• Microsoft-specific enforcement (very common in enterprises) — Many US companies use Microsoft Entra ID (formerly Azure AD) for identity. Microsoft is rolling out mandatory MFA in phases for Azure and Microsoft 365 admin portals:
  • Azure portal and related services: Enforcement ongoing since 2024–2025, with Phase 2 (CLI, PowerShell, APIs) starting October 2025; extensions possible to July 2026 for complex setups.
  • Microsoft 365 admin center: Started phasing in 2025; full blocking of non-MFA users ramps up around February 9, 2026.
  • This affects a huge portion of US enterprises, but only for Microsoft cloud admin access—not every app or on-prem system.
• Industry-specific or contractual mandates:
  • Healthcare (HIPAA) — MFA strongly recommended (and often effectively required via risk assessments) for ePHI access.
  • Finance (GLBA, PCI DSS) — MFA required for certain access to cardholder data or financial systems.
  • Government contractors / defense (NIST SP 800-171, CMMC) — MFA mandatory for accessing Controlled Unclassified Information (CUI), including local/remote access for privileged and non-privileged accounts.
  • Tax professionals (IRS safeguards) — MFA required for systems with taxpayer data.
  • Federal agencies & partners — Phishing-resistant MFA enforced under executive orders and zero-trust mandates (but this is government, not private enterprises).
• Cyber insurance & emerging pressures — Many insurers now require MFA enforcement as a condition for coverage in 2026, making it "mandatory" in practice for businesses seeking affordable policies.
• Software vendors — Starting January 2026, some CISA guidance flags products without default MFA for admins as high-risk (especially for critical infrastructure).

In short: MFA is becoming de facto standard in US enterprises due to Microsoft policies, compliance needs, insurance requirements, and threat landscape—but it's not universally enforced by law everywhere. Small businesses or non-regulated sectors can still operate without it (though it's very risky).