Basel III for Banks & Credit Unions in 2026

The rules that govern how much capital financial institutions hold just shifted again. In March 2026, U.S. regulators scrapped their 2023 Basel III “Endgame” proposal and replaced it with a lighter-touch package — a reversal with real consequences for banks and ripple effects for credit unions. This guide breaks down what Basel III is, what changed in 2026, how it differs for banks and credit unions, what to expect next, and how finance leaders can prepare.

Basel III is the international bank-capital framework created after the 2008 financial crisis. It requires institutions to hold enough high-quality capital and liquid assets to absorb losses without failing or needing a bailout. It sets minimum capital ratios, liquidity buffers, and leverage limits — all backed by rigorous data and reporting standards.

At its core, Basel III rests on three pillars: minimum capital and liquidity requirements (Pillar 1), supervisory review (Pillar 2), and public disclosure (Pillar 3). The primary capital measure is Common Equity Tier 1 (CET1) — mainly common equity and retained earnings — which must total at least 4.5% of risk-weighted assets, rising to roughly 7% once the capital conservation buffer is included. Total capital must reach 8%. A non-risk-weighted leverage ratio (minimum 3%) acts as a backstop, while two liquidity ratios — the Liquidity Coverage Ratio and the Net Stable Funding Ratio — ensure institutions can survive short-term stress and fund themselves over a full year. The 2017 “finalization” of the framework added an output floor that caps how far banks can lower capital using their own internal models.

On March 19, 2026, the Federal Reserve, OCC, and FDIC rescinded the contentious 2023 “Endgame” proposal and issued a revised Basel III package. Where the 2023 version would have raised capital sharply — by roughly 16–19% for the largest banks — the new proposal would modestly lower overall capital while keeping it well above pre-crisis levels. The public comment period closed June 18, 2026.

The March 2026 proposals come in three parts: an Expanded Risk-Based Approach (ERBA) for the largest, most internationally active banks (Categories I and II); a revised Standardized Approach for all other banks, who may also opt into ERBA; and a reworked surcharge for global systemically important banks (G-SIBs). A key simplification removes the “dual stack” — banks will run one set of capital calculations instead of two.

The shift reflects new leadership. After Michael Barr stepped down as the Fed's top supervisor in early 2025, Vice Chair for Supervision Michelle Bowman steered the framework toward “capital neutrality.” Independent analyses from EY and PwC note that the package still tightens risk sensitivity and demands more granular data even as headline capital falls, while Bloomberg frames it as a strategic pivot to keep U.S. banks competitive. Notably, the agencies did not set a firm compliance date, leaving implementation timing open.

Basel III applies directly to banks, which are supervised by the Federal Reserve, OCC, and FDIC. Credit unions fall under a different regulator — the National Credit Union Administration (NCUA) — which runs a separate but comparable regime. Because credit unions can't issue stock to raise capital, their primary yardstick is a net-worth (leverage) ratio rather than risk-weighted ratios.

For credit unions, a 7% net-worth ratio generally defines “well capitalized.” A risk-based capital requirement applies only to “complex” credit unions — those above $500 million in assets — which must hold roughly a 10% risk-based capital ratio or opt into the simpler 9% Complex Credit Union Leverage Ratio. Smaller credit unions face only the net-worth test.

This tiering reflects the cooperative, member-owned model — but the two worlds are converging. After the March 2026 bank proposal, America's Credit Unions urged the NCUA to modernize its capital rules and provide comparable relief — for example, on the treatment of mortgage servicing assets — to preserve parity with banks. The NCUA's own risk-based capital resources confirm the framework was explicitly designed to be comparable to the banking agencies' standards while accounting for credit unions' cooperative character.

The 2026 re-proposal softens the capital hit, but not the operational one. Here's what to expect across the sector:

• Large banks (Categories I & II): A more modest net capital change than the 2023 proposal threatened, but a mandatory rebuild of credit, market (FRTB), and operational risk calculations under ERBA.
• Regional and mid-size banks: A revised Standardized Approach that better aligns capital with actual lending risk, plus the option to adopt ERBA where it's advantageous.
• All institutions: More granular data and attribute collection. The reporting burden rises regardless of where final calibration lands.
• Credit unions: Continued net-worth discipline, with growing pressure on the NCUA to match any capital relief banks receive.
• Cross-border firms: Divergence to manage between U.S. rules, the EU's CRR3 (in force since January 2025), and the UK's Basel 3.1 (effective January 2027).

The through-line is unmistakable: whatever the final numbers, Basel III is raising the bar on data quality, capital and liquidity planning, and auditable reporting. Institutions that treat this as a data and modeling challenge — not just a compliance box to check — will adapt fastest and spend less doing it.

Possibly less than feared. The 2023 proposal drew fierce criticism for potentially curbing mortgage and small-business lending by making those assets more capital-intensive. The 2026 re-proposal walks much of that back — lowering overall capital and better aligning charges with real lending risk — easing, though not eliminating, the concern.

Capital rules shape lending because every loan a bank holds must be backed by capital against its risk weight. When risk weights rise, lending can become more expensive or migrate to less-regulated non-bank lenders. The 2023 Endgame proposal was widely expected to raise costs on residential mortgages, small-business credit, and renewable-energy financing, prompting a national “Stop Basel Endgame” campaign. Regulators heard that feedback: the 2026 Standardized Approach is designed to better match capital to the actual risk of traditional lending, and analysts expect the softer calibration to pull some activity back toward regulated banks. For credit unions — a major source of mortgage credit for low- and moderate-income members — the parallel question is whether the NCUA will grant comparable relief so member lending isn't put at a competitive disadvantage.

Modern Basel III readiness comes down to three capabilities: one trusted source for financial and operational data; the ability to run capital, liquidity, and stress scenarios quickly and repeatedly; and automated, auditable reporting for regulators and management. Fragmented spreadsheets and disconnected point tools simply can't keep pace with expanding data granularity.

First, trusted, aggregated data. The Basel Committee's principles for risk data aggregation and reporting (known as BCBS 239) expect institutions to pull accurate, complete risk and finance data together on demand — something that's nearly impossible when numbers live across dozens of disconnected systems and manual spreadsheets.

Second, dynamic capital and liquidity planning. As requirements shift, finance teams need driver-based models and rolling forecasts they can re-run under multiple scenarios — interest-rate moves, credit stress, changing capital rules — without rebuilding everything from scratch.

Third, accurate, auditable reporting. Pillar 3 disclosures, regulatory filings, and management reporting all demand full transparency from the final number back to the source transaction. Meeting these needs is less about any single Basel calculation and more about the strength of the financial data and planning foundation underneath it.

OneStream unifies financial and operational data on a single platform, giving banks and credit unions one trusted source for capital and liquidity planning, scenario modeling, and regulatory reporting — with full audit trails from report to source. It replaces fragmented spreadsheets and point solutions with the speed, transparency, and agility that Basel III's rising data demands require.

A single, trusted data foundation. OneStream's financial data quality management automates data integration from hundreds of source systems and validates it through guided workflows, with end-to-end audit trails and cell-level auditability that can't be switched off. That directly supports the complete, traceable risk-and-finance data aggregation regulators increasingly expect.

Capital and liquidity planning built for change. Purpose-built for financial institutions, OneStream for financial services supports driver-based modeling tied to economic conditions, interest-rate fluctuations, and regulatory shifts, plus rolling forecasts and scenario analysis at the enterprise planning level. Working alongside an institution's specialized risk and ALM engines, it lets finance teams re-run the plan as Basel calibration evolves rather than starting over each time.

Auditable regulatory and management reporting. With built-in compliance and reporting for US GAAP, IFRS, and local statutory requirements — backed by SOX process controls and 100% audit trails — OneStream helps institutions produce the transparent, defensible disclosures that Basel III's Pillar 3 and regulators demand.

Embedded, finance-specific AI. OneStream's SensibleAI capabilities help surface anomalies in financial data and support forecasting and scenario analysis, so lean finance teams can handle rising data volumes with confidence rather than headcount.

Crucially, because OneStream is a unified, extensible platform rather than a stack of bolted-together point tools, institutions can adapt as rules diverge across jurisdictions and as re-proposals land — without piling on technical debt.

You don't need final rules to start. The highest-value moves are the ones that pay off regardless of where calibration lands:

• Map your data gaps now. Identify where expanding risk-weighted-asset and attribute requirements will outstrip your current data.
• Consolidate onto one finance data foundation. Retire spreadsheet risk and build the “single source of truth” regulators expect.
• Build re-runnable capital, liquidity, and stress models. Make scenario analysis a routine capability, not a quarterly fire drill.
• Automate reporting with audit trails. Cut close and disclosure cycle times while improving defensibility.

Basel III will keep evolving — but the institutions that win are the ones that treat capital, liquidity, and reporting as a connected, data-driven discipline. See how OneStream for financial services helps banks and credit unions turn regulatory change into a strategic advantage.

• Federal Reserve — Agencies request comment on proposals to modernize the regulatory capital framework (March 19, 2026)
• PwC — Capital reform 2026: Basel III endgame and more
• Bloomberg Professional Services — The U.S. Basel III Endgame enters a new phase
• NCUA — Risk-Based Capital Rule Resources
• America's Credit Unions — NCUA urged to modernize capital rules after Basel III shift

This article was written in July 2026 for general information only and does not constitute legal, regulatory, or compliance advice. Institutions should confirm current requirements with their regulators and advisors.