Every trade a bank executes consumes regulatory capital. This is not an abstract accounting concept — it is a hard constraint that determines whether a trade is profitable, whether a desk can grow its book, and whether a bank can afford to be in a particular business at all. Understanding how regulatory capital charges work, and how they translate into the economics of individual transactions, is essential knowledge for anyone working in or around a capital markets trading business.

Risk-Weighted Assets and the Capital Charge

Regulatory capital requirements for banks are expressed as a minimum ratio of capital to risk-weighted assets (RWA). Under Basel III (and its successor framework), a bank must hold Common Equity Tier 1 (CET1) capital of at least 4.5% of its RWA, plus capital conservation and systemic buffers that typically bring the effective minimum to 9–12% of RWA for large institutions. The RWA figure aggregates the capital required across three risk categories: credit risk, market risk, and operational risk.

For a trading book position, the relevant capital charge is the market risk RWA. Under the standardised approach (SA-MR), market risk RWA is calculated using the FRTB Sensitivity-Based Approach — applying prescribed risk weights to the sensitivities of each position to its risk factors. Under the internal models approach (IMA), market risk RWA is derived from the Expected Shortfall calculation for IMA-eligible desks. In both cases, the capital charge is specific to the positions on the book: a position in liquid, hedged instruments generates much lower market risk RWA than a concentrated, unhedged position in illiquid instruments.

From RWA to Capital Cost

The capital charge translates into a cost through the concept of the cost of equity. A bank must hold equity capital against its RWA. That equity capital has a cost — shareholders require a return on the capital they have committed to the bank. The bank's required return on equity (ROE) — typically expressed as a hurdle rate — represents the minimum return a business or transaction must generate to justify the capital it consumes.

If a bank has a cost of equity of 12% and a trade consumes £10 million of CET1 capital (equivalent to, say, £111 million of RWA at a 9% CET1 ratio), then the trade must generate at least £1.2 million of annual revenue (12% × £10 million) simply to cover its capital cost. A trade that generates £1 million of P&L but consumes £10 million of capital is destroying economic value for the bank, even though it is nominally profitable.

RAROC: Risk-Adjusted Return on Capital

Risk-Adjusted Return on Capital (RAROC) is the framework through which banks compare the economic profitability of trades and businesses that consume different amounts of capital. The RAROC formula divides the risk-adjusted revenue of a transaction by the economic capital it consumes:

RAROC = (Revenue – Expected Loss – Operating Cost) / Economic Capital

A transaction with a RAROC above the hurdle rate creates value; one with a RAROC below the hurdle rate destroys it. RAROC is used in several ways: in pricing — to determine whether the terms of a proposed transaction meet the hurdle rate; in portfolio management — to identify which positions or clients are generating or destroying value on a capital-adjusted basis; and in strategy — to evaluate whether particular business lines or products are worth pursuing given their capital intensity.

Front-office traders and salespeople at sophisticated banks have access to capital consumption figures for each transaction. Before pricing a complex derivative, the trader knows not just the hedging cost and the credit spread, but also the capital charge. A transaction that looks marginally profitable on a revenue basis may be clearly unprofitable on a RAROC basis if it is highly capital-intensive — for example, a long-dated equity option where the vega exposure consumes substantial market risk RWA.

The Leverage Ratio

The leverage ratio is a non-risk-sensitive capital constraint that operates alongside the RWA-based framework. Under Basel III, banks must hold Tier 1 capital of at least 3% of total exposures (the exposure measure is broadly equivalent to total assets, with some adjustments for derivatives and off-balance-sheet items). The leverage ratio cannot be gamed by lowering the risk weight on assets — it applies to all assets equally.

For a capital markets bank, the leverage ratio constraint can be more binding than the RWA constraint for low-risk, high-volume businesses. A repo book, for example, involves large notional amounts of government securities with very low credit risk. Under the RWA framework, the capital charge is modest. Under the leverage ratio, the full notional exposure is included in the denominator, consuming leverage capacity. This is one reason why large banks have become more selective about their repo and securities financing businesses post-Basel III: the economics changed when the leverage ratio constraint became binding.

SA-CCR: Counterparty Credit Risk Capital

Derivatives positions also generate counterparty credit risk (CCR) capital charges, reflecting the risk that a counterparty might default on its future obligations. The Basel framework replaced the previous Current Exposure Method (CEM) with the Standardised Approach for Counterparty Credit Risk (SA-CCR) — a more risk-sensitive methodology that better captures the netting and collateral-reducing effects of portfolio-level agreements.

SA-CCR calculates the exposure at default (EAD) for a derivatives portfolio as the sum of the Replacement Cost (RC) — the current mark-to-market exposure — and the Potential Future Exposure (PFE) — a regulatory estimate of how much the exposure might increase over the remaining life of the transaction. The PFE calculation uses prescribed supervisory factors for each asset class and tenor bucket. The resulting EAD is then multiplied by the counterparty's risk weight (from a credit ratings lookup or the standardised credit risk weights) to produce the CCR RWA.

SA-CCR gives a material capital advantage to centrally cleared transactions — the CCP's risk weight is typically 2% compared to 20–100% for uncleared counterparties — and to transactions with comprehensive netting and collateral agreements. This creates a direct incentive for banks and their clients to clear standardised derivatives and to post margin on uncleared trades. Capital cost is therefore a key driver of the continuing migration of derivatives to central clearing.

How Traders Think About Capital

In a well-run capital markets bank, the capital charge is embedded in the pricing and profitability framework at the trading desk level. Desks are allocated a capital budget — an amount of RWA or regulatory capital they are permitted to consume — as part of the annual planning process. Consuming capital efficiently (generating maximum revenue per unit of RWA) is a core performance objective alongside absolute P&L.

In practice, this manifests in several ways. Traders actively manage their RWA footprint: hedging positions that carry disproportionate capital charges, seeking to novate positions to more capital-efficient counterparties (for example, a bilateral derivative can be cleared through a CCP to reduce CCR RWA), and avoiding transactions where the capital cost exceeds the available margin. Sales teams factor capital cost into client pricing: a transaction quoted to a client at a spread that looks competitive on its face may carry a capital charge that makes it uneconomic for the bank, requiring the salesperson to renegotiate terms or walk away.

Capital efficiency has become as important as market risk management in determining the shape of a bank's trading book. The post-Basel III environment has materially changed which businesses are viable at scale, which products can be offered at competitive prices, and which clients are worth serving. Understanding the capital framework is therefore not just a regulatory compliance matter — it is central to understanding the business of capital markets.