Basel III is the international regulatory framework for bank capital adequacy, stress testing, and liquidity — developed by the Basel Committee on Banking Supervision and implemented in the US through Federal Reserve and FDIC rules. It sets minimum capital ratios and liquidity buffers that directly affect how much credit banks can extend.
Basel III was developed in response to the 2007–2009 global financial crisis, which exposed dangerous under-capitalization and liquidity mismatches in major banks worldwide. The Basel Committee on Banking Supervision (BCBS), hosted by the Bank for International Settlements (BIS), published the framework in 2010–2011. US implementation came through Federal Reserve, OCC, and FDIC rulemaking, fully phased in by 2019. The three core pillars: (1) Minimum capital requirements — banks must hold common equity Tier 1 (CET1) capital of at least 4.5% of risk-weighted assets, Tier 1 capital of 6%, and total capital of 8%. A capital conservation buffer of 2.5% (CET1) sits on top of the minimums. Large global banks face an additional G-SIB surcharge of 1–3.5%. (2) Supervisory review — regulators conduct Comprehensive Capital Analysis and Review (CCAR) and Dodd-Frank Act Stress Tests (DFAST) for large banks, ensuring capital is adequate under severe scenarios. (3) Market discipline — enhanced disclosure requirements so markets can assess bank capital positions. Basel III's liquidity standards — the Liquidity Coverage Ratio (LCR) and Net Stable Funding Ratio (NSFR) — require banks to hold sufficient high-quality liquid assets to survive a 30-day stress scenario and fund their activities over a one-year horizon, respectively. For small business borrowers, Basel III matters because higher capital requirements make SMB lending more expensive. SMB loans are risk-weighted at 100% under standardized approaches, meaning every $1 of SMB loans requires $0.08–$0.105 of regulatory capital backing. When capital is constrained, banks prioritize lower-RWA assets. 'Basel IV' (or Basel III 'endgame') rules proposed in 2023 would further increase RWA calculations for many loan types.
Basel III raises the cost of bank capital, which makes SMB lending more expensive relative to lower-risk assets. When banks are near their capital minimums — or when regulators are tightening standards — SMB approval rates fall and pricing rises. Banks with strong capital ratios (CET1 well above 10%) have more flexibility to extend credit. If you're seeing rejections from your bank, checking public call report data at the FDIC's BankFind database can reveal whether capital constraints are a factor.
Basel II (2004) focused on refining risk-weight calculations and introduced internal ratings-based approaches for large banks. Basel III (2010–2011) responded to the financial crisis by dramatically increasing minimum capital levels, adding the capital conservation buffer and G-SIB surcharge, and introducing mandatory liquidity standards (LCR and NSFR). Basel III also improved the quality of capital — focusing on common equity rather than hybrid instruments that proved unreliable in 2008.
US community banks (generally under $10B in assets) follow a simplified capital framework. They must meet the same basic Tier 1 and total capital minimums, but are exempt from the most complex Basel III provisions — including the LCR, NSFR, and DFAST stress tests. The Community Bank Leverage Ratio (CBLR) framework, introduced in 2020, allows qualifying community banks to use a simple leverage ratio (9%) instead of risk-weighted capital calculations.
The Basel Committee finalized additional reforms in 2017 — sometimes called 'Basel IV' or the Basel III endgame — that constrain banks' use of internal models and introduce output floors (no bank can hold less than 72.5% of the capital calculated using standardized approaches). US regulators proposed implementation rules in 2023. If finalized, the rules would increase required capital for many large banks and could tighten SMB credit availability further. Cite: Federal Reserve Basel III endgame proposal at federalreserve.gov.