Clean Price vs. Dirty Price
Prix pied de coupon vs prix plein coupon in French
Quick definition
The clean price is a bond's quoted price, excluding interest accumulated since the last coupon. The dirty price (or invoice price) is what you actually pay: the clean price plus accrued interest. Screens quote clean; your account is charged dirty.
Two prices for the same bond
Every bond trade involves two numbers. The clean price is the one you see quoted on trading screens, in the media and on your brokerage's bond inventory. The dirty price, also called the invoice price or full price, is the amount that actually leaves your account: the clean price plus the accrued interest built up since the last coupon payment.
The logic is fairness. A bond pays its coupon in lumps, typically every six months, but the interest is earned continuously. If you buy a bond four months into a six-month coupon period, the seller has earned four months of that coupon and you will collect all six months' worth on the payment date. The accrued interest you pay at purchase compensates the seller for their four months.
Why the market quotes clean
Accrued interest grows mechanically, day by day, at a completely predictable pace. It says nothing about whether the bond became more or less attractive. Quoting the clean price strips out that mechanical drift so a price change on the screen reflects a true market move: shifting interest rates, changing credit quality, supply and demand.
If markets quoted dirty prices instead, every bond would appear to rally a little every single day and then crash on each coupon date, drowning the real signal. The clean convention keeps quotes comparable from one day to the next, and comparable to measures like yield to maturity that are calculated from market conditions rather than the calendar.
The sawtooth pattern
Plot both prices over time for a bond whose market conditions never change and the difference becomes obvious. The clean price traces a smooth, flat line. The dirty price climbs a little every day as interest accrues, then drops by exactly the coupon amount on the payment date, when the accrued interest resets to zero, and starts climbing again.
Chart a year of dirty prices for a semi-annual bond and you get two big teeth. That sawtooth is pure mechanics, not market news, and it is exactly the noise the clean-price convention removes.
What you see on your brokerage confirmation
When you buy a bond through a Canadian brokerage, the confirmation slip breaks the trade into the clean price, the accrued interest and the total (dirty) amount. Do not be surprised that the cash withdrawn from your account exceeds the quoted price times the quantity: the difference is the accrued interest, and you get it back as part of the very next coupon payment.
In Canada
Canadian bonds accrue interest on the Actual/Actual (Canada) day count convention, which is the convention our Bond Calculator uses. Day count rules differ across markets (US corporate bonds, for example, commonly use 30/360), so the accrued interest on otherwise similar bonds can differ slightly across borders.
Canadian bond quotes are expressed per $100 of face value, so a quote of $98.50 means you pay $985 of clean price per $1,000 of face value, plus accrued interest.
Worked example
A Government of Canada bond is quoted at $98.50, which is the clean price per $100 of face value. Since the last semi-annual coupon, $1.20 per $100 of interest has accrued. The dirty price is therefore $98.50 + $1.20 = $99.70.
You buy $10,000 of face value. Your brokerage charges 100 times $99.70, so $9,970 leaves your account: $9,850 for the bond itself and $120 of accrued interest to the seller. On the next coupon date you receive the full six-month coupon, which repays your $120 and adds the interest earned during your own holding period.
Related terms
Reviewed by Alexandre Bernier, CFP®, CIM®, PFP®·Updated July 2026