Clean Price vs. Dirty Price Bond Spread
The Formal Definition
The structural difference between a bond's quoted market price (clean price, which excludes accrued interest) and the actual total cash invoice price required for settlement (dirty price, which adds interest accrued since the previous coupon payment date).
Dirty Price (Invoice Price) = Clean Price (Quoted Price) + [ Annual Coupon × (Days Since Last Coupon / Days in Coupon Period) ]
Cole Barrett's Reality Check
The Unvarnished Bottom Line"Looking at bond quotes can be confusing if you don't know about accrued interest. A bond might be quoted on your screen at a clean price of $98. But when you hit buy, your broker bills you $101. That extra $3 isn't a hidden broker fee; it's accrued interest owed to the previous bondholder for the days they held the bond since the last coupon. The dirty price is the real cash that leaves your account."
Interactive Simulator: Test the Math
Real-World Example: Scenario Breakdown
Examining the real numbers for: Purchasing 10 corporate bonds ($10,000 par) with an 8.0% annual coupon paid semi-annually, executed 150 days into a 180-day coupon cycle
| Execution Metric | Informed Dirty-Price Modeler | Clean-Price Blind Retail Trader |
|---|---|---|
| Fee / Rate | $1/bond institutional ticket | $0 advertised fees |
| Spread / Buffer | Quoted clean price: $99.00 ($9,900); calculated accrued interest: $10,000 × 8% × (150 / 360) = $333.33 | Looked only at the clean quote of $99.00 and left exactly $9,950 in cash in their account |
| Execution / Status | Anticipated the total cash invoice price ($10,233.33) and budgeted account cash accordingly | Broker processed the trade at the dirty price of $10,233.33, creating an unexpected cash deficit |
| Total Cost / Result | Managed cash settlement without margin surprises | Incurred margin borrowing interest due to unexpected accrued interest settlement |
How Brokers Weaponize This Term
Always verify the 'Dirty Price' or 'Total Settlement Amount' before clicking confirm on any secondary market bond order. Clean prices are used for charting convenience, but the dirty price is the actual cash required to settle the trade.
Broker Evaluation Matrix
Cole Approves
Interactive Brokers: Displays both clean and dirty prices side-by-side on all secondary bond order tickets, showing exact accrued interest calculations before submission.
Read Audit →Cole Flags / Avoids
Retail Platforms with Hidden Bond Markups: Hides accrued interest and embeds secondary markups directly into the quoted bond price, making true bond yields difficult to calculate.
View Trap Details →Frequently Asked Questions
Why are bonds quoted at clean prices instead of dirty prices?
Because accrued interest grows every day until the coupon is paid, causing dirty prices to follow a saw-tooth pattern. Quoting clean prices strips out this daily interest drift, allowing traders to see true yield and credit changes.
Do Treasury bills have a clean and dirty price?
No. Treasury bills are zero-coupon instruments issued at a discount to par value that do not pay recurring coupons, meaning their quoted price is their actual settlement price.