Clean Price vs Dirty Price of Bonds: TIRM Guide (2026)

When a government bond changes hands on the NDS-OM platform, two very different numbers describe what it is worth — and confusing them is one of the costliest slips a treasury dealer can make. Grasping clean price vs dirty price is essential for anyone settling G-Sec or corporate bond trades in India, whether you sit on the dealing desk, in the back office, or are preparing for the IIBF Treasury Investment and Risk Management (TIRM) exam. The quoted market price is almost never the amount of cash that actually leaves the buyer's account.

The gap between the two is accrued interest — the coupon that has silently built up since the last interest payment date. Get the accrued-interest arithmetic wrong and your settlement amount, your profit-and-loss, and your regulatory valuation all drift off. This guide breaks down what each price means, how they connect, why Indian markets quote one but settle on the other, and the exam traps that catch candidates every year.

💰 What Clean Price and Dirty Price Actually Mean

The clean price is the price of a bond excluding any interest that has accrued since the previous coupon date. It is the "headline" figure you see on a dealer screen, in a FIMMDA daily valuation sheet, or in a newspaper bond table. Because it strips out the accrued coupon, the clean price moves smoothly with changes in yield, credit spread and time to maturity, which makes it the fair basis for comparing one bond against another.

The dirty price — also called the invoice price, gross price, or settlement price — is the amount the buyer actually pays. It equals the clean price plus accrued interest. On the day a bond is bought, the new holder must compensate the seller for the portion of the next coupon that the seller has effectively "earned" by holding the bond up to the settlement date. That reimbursement is bundled into the dirty price so that the cash actually changing hands reflects true economic value.

A useful mental model: the clean price is the value of the bond as an instrument, while the dirty price is the value of the bond plus the running coupon meter attached to it. Understanding the mechanics of the underlying financial markets where these instruments trade makes the distinction far more intuitive.

💡 Exam Tip: The clean price is what you quote; the dirty price is what you pay. If a TIRM question asks for the cash settlement amount, it wants the dirty price every time.

🧮 How Accrued Interest Bridges the Two Prices

Accrued interest is the single term that separates the clean price from the dirty price, so mastering its formula is non-negotiable. The standard calculation is:

Accrued Interest = Face Value × Coupon Rate × (Days since last coupon ÷ Days in the coupon period)

For Indian Government securities, FIMMDA prescribes the 30/360 day-count convention, meaning each month is treated as 30 days and a full year as 360 days. Take a ₹100 face-value G-Sec carrying a 7.10% annual coupon paid semi-annually (so ₹3.55 per half year). If 90 days of a 180-day coupon period have elapsed, accrued interest is ₹3.55 × (90 ÷ 180) = ₹1.775. A buyer paying a clean price of ₹99.20 therefore settles at a dirty price of ₹100.975 per ₹100 face value.

Two behaviours follow directly. First, accrued interest grows in an almost straight line each day between coupon dates, so the dirty price ratchets upward daily even when the clean price is flat. Second, on the coupon payment date the coupon is disbursed and accrued interest instantly resets to zero — at that instant the clean price and dirty price are identical. Different day-count conventions (actual/actual, actual/365) apply to other instruments, so a dealer working across money-market and bond desks must always confirm which convention governs the trade. This precision sits at the heart of sound risk analysis and control.

⚠️ Common Mistake: Candidates apply an actual/365 day count to a G-Sec. Indian sovereign bonds use 30/360 for accrued interest — using the wrong convention throws off the dirty price and the settlement figure.

📊 Clean Price vs Dirty Price: A Side-by-Side View

The two prices serve distinct purposes across trading, settlement and accounting. The table below contrasts them on the dimensions that matter most for a treasury professional and for the TIRM exam.

Notice the saw-tooth behaviour: the dirty price climbs steadily as interest accrues, then drops sharply by the coupon amount on the payment date, while the clean price glides along a smooth path. This is why front-office screens and the daily valuation feeds used for marking positions rely on the clean price — it isolates genuine market movement from the mechanical drift of accrued interest. Traders analysing relative value across the SLR and non-SLR investments book always compare clean prices, never dirty ones.

🏦 Why Indian Bond Markets Quote Clean but Settle Dirty

Global convention — followed by India's CCIL-settled G-Sec market — is to quote the clean price and settle on the dirty price. The logic is practical. If bonds were quoted dirty, the headline price would jump around simply because time passes and coupon accrues, making it impossible to judge whether a bond had genuinely cheapened or richened. Quoting clean lets dealers and the RBI-supervised market compare securities on a like-for-like basis regardless of where each sits in its coupon cycle.

Yet settlement must use the dirty price, because the seller is entitled to be paid for interest earned during their holding period. When CCIL nets and settles trades, it computes the invoice amount as clean price plus accrued interest for each leg. This same split flows into a bank's books: the clean price feeds mark-to-market valuation and the profit-and-loss reserve, while accrued interest is booked separately as "interest accrued but not due." Getting this segregation right keeps a bank compliant with RBI's investment classification and valuation norms, and it interlocks with disciplines such as value at risk in treasury portfolios and the wider study of treasury and risk management.

For dealers, one more nuance matters. Because Macaulay duration vs modified duration measures are computed from the bond's cash flows and yield, they relate to the clean-price valuation, whereas the cash you fund on the settlement date is the dirty price. Confusing the two is a classic source of funding and P&L reconciliation errors — a theme that recurs throughout the study of money market instruments too.

📌 Remember: Quote clean, settle dirty. Clean price = comparison and valuation; dirty price = cash and funding. On the coupon date they meet at exactly the same number.

Candidates who want a deeper grounding in how these obligations are met by market makers should also review the role of primary dealers in India, who quote two-way clean prices in the G-Sec market every trading day.

🧠 Practice MCQs: Clean Price vs Dirty Price

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❓ Frequently Asked Questions

Mastering the clean price vs dirty price distinction is a foundational skill for treasury settlement, accurate P&L and RBI-compliant valuation — and it is nearly guaranteed to feature in the TIRM paper. Reinforce it with full-length practice before exam day: explore the TIRM & CAIIB course → and put your accrued-interest arithmetic to the test.