Basel IV Explained: Credit Risk, Output Floor, and Impact

Basel IV is the banking industry’s informal name for a package of capital reforms the Basel Committee on Banking Supervision finalized in December 2017. The Committee itself titles the package “Basel III: Finalising post-crisis reforms,” but the changes are broad enough that bankers, regulators, and analysts generally treat them as a new generation of rules.¹ The reforms rewrite how banks measure credit risk, operational risk, and market risk, and they cap the benefit any bank can extract from its own internal models through a hard floor set at 72.5% of the standardized result.

Why the Reforms Exist

After the 2008 financial crisis, regulators found that two banks holding essentially the same portfolio could report very different capital ratios simply because they used different internal models. The Basel Committee’s own studies confirmed a troubling degree of variability in risk-weighted asset calculations, and confidence in reported capital numbers eroded.¹ If ratios cannot be compared across banks, they stop working as a safety signal. The 2017 reforms attack that problem from three directions at once: they make standardized approaches more risk-sensitive, they constrain what internal models can do, and they set a floor beneath model-derived results.

Credit Risk: A New Standardized Approach

The revised standardized approach for credit risk replaces broad, blunt categories with a more granular structure. It touches mortgages, corporate lending, retail exposures, and the due diligence banks must perform on every counterparty.

Mortgages Tied to Loan-to-Value

The old rules assigned most residential mortgages a flat 50% risk weight regardless of the borrower’s equity. That is gone. Risk weights now scale directly with the loan-to-value ratio. For owner-occupied homes where repayment does not depend on rental income, the schedule runs from 20% at an LTV of 50% or below, to 25% between 50% and 60%, 30% from 60% to 80%, 40% from 80% to 90%, 50% from 90% to 100%, and 70% when the borrower is underwater.²

Investment properties and other mortgages where repayment depends on the property’s cash flow carry higher weights at every LTV band, ranging from 30% at low LTV up to 105% when the borrower owes more than the property is worth.² Banks holding large portfolios of high-LTV or investment-property loans need meaningfully more capital than before.

Corporate and Retail Exposures

Unrated corporate borrowers generally receive a 100% risk weight. Banks in jurisdictions that do not rely on external ratings can assign a lower 65% weight to borrowers they classify as investment grade after internal analysis, provided the borrower can demonstrate the capacity to meet its obligations even in a downturn.²

Retail exposures now split by repayment behavior. Credit card holders who have paid their balance in full every month for the previous 12 months qualify as “transactors” and receive a 45% risk weight. Other qualifying retail exposures carry 75%, and retail exposures that fall outside the regulatory retail criteria carry 100%.² That 30-point gap gives banks a capital incentive to lend to borrowers with cleaner repayment habits.

Mandatory Due Diligence

Banks must now conduct their own assessment of each counterparty at origination and at least annually afterward. Passive reliance on external ratings is no longer enough. Banks must review financial performance, analyze trends, and be able to justify the risk weight assigned to any exposure to their supervisor. The sophistication of the analysis should match the bank’s size and complexity.² Building an annual due diligence process across an entire loan book is a meaningful operational cost that many banks underestimate.

Operational Risk: One Formula for Everyone

Operational risk covers cyberattacks, internal fraud, legal settlements, system failures, and similar events. Before these reforms, the largest banks could use their own Advanced Measurement Approaches to model operational risk capital. Those internal models are eliminated. Every bank now uses a single standardized calculation built around a metric called the Business Indicator, which is a financial-statement proxy for the scale of a bank’s revenue-generating activities and, by extension, its exposure to operational failures. The Business Indicator is multiplied by regulatory coefficients that rise with bank size, producing the Business Indicator Component.³

A second layer, the Internal Loss Multiplier, adjusts that result based on the bank’s actual loss history over the previous ten years. A bank whose historical losses run high relative to its Business Indicator Component faces a multiplier above one; a bank with a clean loss record gets a multiplier below one. National regulators may set the multiplier at one for all banks in their jurisdiction, which would make the calculation purely size-based.³ The important shift is that banks no longer build bespoke models to argue for lower operational risk capital; everyone starts from the same formula.

The Output Floor

The output floor is probably the single most consequential piece of the reforms. Banks that use internal models for risk-weighted assets often produce significantly lower numbers than the standardized approaches would. The floor caps that advantage: a bank’s total risk-weighted assets under internal models cannot fall below 72.5% of what the standardized approaches produce.¹

In practice, a bank runs two parallel calculations across its entire balance sheet. One uses whatever internal models it has approval to use. The other uses only standardized approaches for credit, market, and operational risk. If the internal model figure falls below 72.5% of the standardized figure, the bank must use the floored amount for capital purposes. The bank’s minimum capital requirement is based on whichever number is higher, which directly increases how much Tier 1 capital it must hold.⁴

The floor phases in gradually. Under the original Basel Committee timeline it was set to start at 50% in January 2022 and rise 5 percentage points each year, reaching 72.5% by January 2027. The COVID-19 pandemic pushed the schedule back one year: the phase-in began at 50% in January 2023 with annual step-ups targeting 72.5% by January 2028.⁵⁶ For 2026, the applicable floor level is 70%. Banks with large internal-model portfolios feel the pressure more with each annual increase.

Market Risk and the Trading Book

The market risk overhaul, known as the Fundamental Review of the Trading Book (FRTB), rebuilds how banks calculate capital for trading activities. Old value-at-risk models are replaced by expected shortfall models, which better capture extreme losses in the tail of the distribution. The framework also draws a firmer boundary between the trading book and the banking book, making it harder to shift assets between them to minimize capital charges.⁷

Banks that want to use internal models for market risk must now obtain approval at the individual trading desk level rather than institution-wide. Each desk must pass ongoing profit-and-loss attribution tests and backtesting against realized results. Desks that fail lose their internal model approval and revert to the standardized approach until they requalify.⁷

Credit Valuation Adjustment Risk

Credit valuation adjustment (CVA) risk reflects the possibility that the market value of a bank’s derivative contracts changes because its counterparty’s creditworthiness changes. The revised framework eliminates internal models for CVA and offers two options: a basic approach and a standardized approach. Banks default to the basic approach unless they receive supervisory approval for the more complex standardized approach, which requires a dedicated CVA desk. Banks with a total notional of non-centrally cleared derivatives of €100 billion or less can skip the formal calculation entirely and set the CVA charge at 100% of their counterparty credit risk capital charge.⁸ For the largest derivatives dealers, the new framework generally increases CVA capital requirements.

Leverage Ratio Buffer for the Largest Banks

All banks subject to the framework must maintain a minimum Tier 1 leverage ratio, calculated as Tier 1 capital divided by total exposure. The exposure measure captures on-balance-sheet items at gross accounting values plus off-balance-sheet commitments, with no netting and no credit for collateral.⁹ Because the leverage ratio ignores risk weighting, it serves as a backstop against models that may understate true exposure.

Global Systemically Important Banks face an additional leverage ratio buffer on top of the minimum, set at 50% of the bank’s risk-weighted higher-loss absorbency surcharge. A G-SIB required to hold a 2% risk-weighted surcharge would therefore face a 1% leverage ratio buffer. Falling short of the buffer triggers escalating restrictions on how much of its earnings the bank can distribute as dividends, share buybacks, or bonuses, with retention ratios that can rise to 100% and freeze distributions entirely.¹⁰

Where Implementation Stands

The Basel Committee sets international standards, but each country must adopt them through its own legislation and regulation. As of late 2025, only 8 of the Committee’s 20 member jurisdictions had fully implemented the final reforms, despite the original target of January 2023.

European Union

The EU transposed most of the reforms through the Capital Requirements Regulation III (CRR3) and Capital Requirements Directive VI (CRD6). Most CRR3 provisions took effect on January 1, 2025. The FRTB market risk rules have been delayed twice; the European Commission adopted a second delegated act in June 2025 pushing their application date to January 1, 2027, citing the need to align with other major jurisdictions and preserve a level playing field for EU banks.¹¹

United States

The U.S. path has been turbulent. Federal banking agencies proposed an initial version of the rules (widely called “Basel III Endgame”) in July 2023, but that proposal drew intense industry opposition and was formally rescinded. On March 19, 2026, the agencies issued three new re-proposals. One targets the largest internationally active banks and implements the core Basel III revisions for credit, market, and operational risk. Another applies to all other banks and focuses on aligning capital requirements for traditional lending with actual risk. A third, from the Federal Reserve, would revise how systemic risk surcharges are calculated for G-SIBs.¹² Comments were due by June 18, 2026, and no final effective date has been set.

United Kingdom

The UK’s Prudential Regulation Authority announced in January 2025 that its implementation (called “Basel 3.1” in the UK) would be delayed by one year to January 1, 2027. Internal model requirements for market risk could be pushed out an additional year to January 2028.

What It Means for Banks and Borrowers

The combined effect of these reforms shifts capital requirements in ways that flow through to lending decisions. Granular mortgage risk weights mean banks concentrated in low-LTV, owner-occupied lending could see capital requirements drop compared to the old flat 50% weight, while lenders focused on high-LTV or investment-property loans face higher charges and often adjust pricing accordingly.

The output floor hits hardest at banks that have relied on internal models to produce low risk-weight estimates. For those institutions, the phase-in to 72.5% may require raising substantial new capital or shrinking certain business lines. Banks that already use standardized approaches feel little direct impact from the floor, though the revised calculations still change their capital math for individual asset classes.

The operational risk overhaul creates particular pressure on banks with clean loss histories that had benefited from low internal model results. Depending on how their national regulator treats the Internal Loss Multiplier, these banks may face higher charges under the new formula than they did under their old bespoke models. Banks with significant historical losses may find the new approach produces results comparable to what they were already holding.

For borrowers, the most visible consequence shows up in pricing. Where capital requirements for a particular loan type rise, banks tend to pass some of that cost through as higher interest rates or tighter lending standards. Where requirements fall, competitive pressure among lenders usually pushes rates down over time.

1
Bank for International Settlements. Basel III: Finalising Post-Crisis Reforms
2
Bank for International Settlements. Basel Framework CRE20 – Standardised Approach: Individual Exposures
3
Bank for International Settlements. Basel Framework OPE25 – Standardised Approach
4
Bank of England. CP16/22 – Implementation of the Basel 3.1 Standards: Output Floor
5
Bank for International Settlements. Finalising Basel III In Brief
6
ABA Banking Journal. Implementation of Basel IV Standards Delayed
7
Bank for International Settlements. Minimum Capital Requirements for Market Risk
8
Bank for International Settlements. Basel Framework MAR50 – Credit Valuation Adjustment Framework
9
Bank for International Settlements. Basel Framework LEV30 – Exposure Measurement
10
Bank for International Settlements. Basel Framework LEV40 – Leverage Ratio Requirements for Global Systemically Important Banks
11
European Commission. Commission Proposes to Postpone by One Additional Year the Market Risk Prudential Requirements Under Basel III
12
Office of the Comptroller of the Currency. Agencies Request Comment on Proposals to Modernize Regulatory Capital Framework