Clean Price and Dirty Price

What Are Clean Price and Dirty Price?

In bond markets, two price concepts coexist. The clean price (also called the flat or quoted price) is the bond's market value excluding any accrued interest. The dirty price (also called the full or invoice price) is the clean price plus accrued interest, representing the total amount the buyer pays at settlement.

The formula is straightforward: Dirty Price = Clean Price + Accrued Interest. Bond trading screens, financial data providers, and news reports display clean prices. Settlement statements show dirty prices.

Why It Matters for Markets

The clean/dirty price distinction is fundamental to how bond markets operate. Without it, bond price charts would show a sawtooth pattern: gradually rising as coupon interest accrues, then dropping sharply on each coupon payment date. This pattern would obscure genuine market-driven price movements and make technical analysis, relative value comparisons, and portfolio tracking unreliable.

By separating the predictable accrued interest component from the market-driven clean price, the convention allows traders to focus on what matters: changes in yield, credit perception, and supply/demand dynamics. A clean price decline indicates genuine market weakness, not just a coupon payment reducing accrued interest.

For portfolio valuation purposes, both concepts matter. The total market value of a bond holding equals the dirty price times the number of bonds held. Investment performance calculations must use dirty prices to capture total return accurately, including the income component.

Practical Implications

When comparing bonds for relative value, always use clean prices or yields, never dirty prices. Two bonds with identical fundamentals but different coupon payment dates will have different dirty prices simply due to different accrued interest amounts.

When calculating total return on a bond investment, the dirty price paid at purchase and the dirty price received at sale (or maturity) determine the actual profit or loss. The difference between purchase and sale dirty prices, plus any coupon payments received during the holding period, equals the total dollar return. This is why accurate tracking of accrued interest at both entry and exit is essential for performance measurement. The distinction is particularly important for institutional investors who need to calculate precise returns for reporting and benchmarking purposes.