What Is a Bond? Coupons, Par, and Accrued Interest

Bonds are one of the most widely held investments on the planet — yet most new investors can't explain how the cash flows actually work. That gap leads to confusion when reading quotes, comparing yields, or understanding what you're actually buying. The core idea is simple: a bond is a loan you make to a borrower, and in return you get regular interest payments plus your principal back at maturity.

The practical starting point isn't memorizing formulas. It's understanding four terms — coupon, par value, maturity, and accrued interest — and seeing how they connect in a real cash flow example.

---

Bond Basics (The Four Terms You Need)

Before anything else, lock in these definitions. Every bond conversation builds on them.

Par value (also called face value) is the amount the bond issuer promises to repay at maturity. For most bonds, this is $1,000 per bond. When someone says a bond is "trading at par," they mean its market price equals $1,000. When it trades above par (say $1,050), that's called a premium. Below par (say $970), that's a discount.

Coupon rate is the annual interest rate the issuer pays, expressed as a percentage of par value. A 5% coupon on a $1,000 par bond means the issuer pays you $50 per year in interest. The word "coupon" comes from the old days when bondholders literally clipped paper coupons and mailed them in to collect interest (a detail that makes the term less mysterious).

Maturity is the date when the issuer repays your par value. A 10-year bond issued today matures in 2036. At maturity, you receive your final coupon payment plus the full $1,000 par value. Until that date, the bond's market price can fluctuate — but the maturity payment is fixed (assuming the issuer doesn't default).

Accrued interest is the interest that has built up since the last coupon payment but hasn't been paid yet. This matters when bonds trade between coupon dates (which is most of the time). More on this below — it's where most beginner confusion lives.

Why this matters: these four terms define every bond's cash flow. Once you understand them, you can read any bond quote, compare any two bonds, and know exactly what you're getting paid and when.

---

How Coupon Payments Work (Your Income Stream)

The coupon is your income as a bondholder. Here's how the mechanics play out.

Most U.S. bonds pay coupons semiannually (twice per year). So a 5% coupon on $1,000 par doesn't arrive as one $50 payment — you receive $25 every six months. Some international bonds pay annually, but the semiannual convention dominates the U.S. market.

The calculation:

Semiannual coupon payment = (Coupon Rate × Par Value) / 2

Example:

• Coupon rate: 5%
• Par value: $1,000
• Annual coupon: 5% × $1,000 = $50
• Semiannual payment: $50 / 2 = $25 every six months

The coupon rate is fixed at issuance and doesn't change over the life of the bond (for fixed-rate bonds, which are the vast majority). If you buy a 5% coupon bond, you get $50 per year regardless of what happens to market interest rates. That predictability is the entire appeal of bonds for income-focused investors.

The point is: your coupon payments are contractual obligations. The issuer owes you that money on a set schedule, unlike stock dividends (which can be cut at any time). This is why bonds are called "fixed income."

---

Coupon vs. Yield (They're Not the Same Thing)

New investors often confuse the coupon rate with the yield. They're related but different, and the distinction matters as soon as you buy a bond at anything other than par.

Coupon rate is fixed — it's the percentage printed on the bond. Current yield changes with the market price.

The calculation:

Current Yield = Annual Coupon Payment / Market Price × 100

Example — bond trading at a discount:

• 5% coupon, $1,000 par = $50 annual coupon
• Market price: $950
• Current yield: $50 / $950 = 5.26%

You're still getting $50 per year, but because you paid less than par, your effective return on the money you invested is higher than 5%.

Example — bond trading at a premium:

• Same 5% coupon, $1,000 par = $50 annual coupon
• Market price: $1,030
• Current yield: $50 / $1,030 = 4.85%

Same $50 in income, but you paid more, so your effective yield is lower.

The lesson worth internalizing: when bond prices go up, yields go down — and vice versa. This inverse relationship is the single most important concept in bond investing. You'll see it referenced constantly in market commentary (when someone says "yields are rising," they mean bond prices are falling).

There's a more complete measure called yield to maturity (YTM) that factors in the gain or loss you'll experience when the bond matures at par. If you buy at $950 and hold to maturity, you get $1,000 back — that $50 capital gain boosts your total return beyond what current yield shows. YTM captures both the coupon income and the price adjustment at maturity. For now, just know it exists and that it's the most complete yield measure.

---

Par Value and Maturity (Your Principal Returned)

Par value and maturity work together to define the bond's endpoint.

At maturity, the issuer pays you par value (typically $1,000) regardless of what you originally paid for the bond. If you bought at $950, you receive $1,000 — a $50 gain. If you bought at $1,030, you receive $1,000 — a $30 loss on principal (offset, ideally, by the higher coupon income you collected along the way).

This is why maturity date matters for your strategy. If you plan to hold a bond to maturity, short-term price fluctuations are irrelevant — you know exactly what you'll receive. If you might need to sell before maturity, the market price (which moves daily) determines your return.

Typical maturity ranges:

• Short-term: 1–3 years
• Intermediate-term: 3–10 years
• Long-term: 10–30 years

Why this matters: longer maturities mean more exposure to interest rate changes. A 30-year bond's price swings far more than a 2-year bond's when rates move. This sensitivity is called duration — a topic worth exploring once these basics are solid (see Bond Math Basics: Price/Yield Relationship for the full picture).

---

Accrued Interest (Why Your Settlement Price Differs From the Quote)

This is the concept that trips up most beginners — and even some experienced investors.

Bonds pay coupons on specific dates (say January 15 and July 15). But bonds trade every business day. So what happens when you buy a bond on March 1, halfway between coupon dates?

The seller has held the bond for 45 days since the last coupon (January 15 to March 1). During those 45 days, interest has been accruing — the seller earned it but hasn't received a payment yet. When you buy, you pay the seller for those 45 days of accrued interest on top of the quoted market price. Then, on the next coupon date (July 15), you receive the full six months of coupon income — even though you only held the bond for part of that period.

The calculation:

Accrued Interest = (Annual Coupon / 2) × (Days Since Last Coupon / Days in Coupon Period)

Example:

• 5% coupon, $1,000 par, semiannual payments
• Semiannual coupon: $25
• Days since last coupon: 45
• Days in coupon period: 180
• Accrued interest: $25 × (45 / 180) = $6.25

If the bond's quoted (or "clean") price is $980, your actual settlement cost (the "dirty" price) is $980 + $6.25 = $986.25.

The point is: the price you see quoted isn't the price you pay. Bond quotes show the "clean price" (without accrued interest). Your actual cost includes accrued interest — always.

A note on day-count conventions: Different bond types count days differently. Corporate bonds use the 30/360 convention (assumes every month has 30 days and every year has 360). U.S. Treasuries use actual/actual (real calendar days). The difference is small in most cases, but it's worth knowing that these conventions exist so you aren't surprised when the accrued interest calculation doesn't match your mental math exactly.

---

A Complete Cash Flow Example (Putting It All Together)

Here's what owning one bond looks like from purchase to maturity.

Your bond:

• Par value: $1,000
• Coupon rate: 5% (semiannual payments)
• Maturity: 3 years
• Purchase price: $980 (discount to par)
• Accrued interest at purchase: $6.25

Your cash flows:

You paid $986.25 and received $1,150.00 over three years. That $163.75 net gain comes from two sources: $150 in coupon income (6 payments × $25) and $13.75 from buying below par ($1,000 – $986.25). This is the bond investor's total return in action.

---

Bond Basics Checklist (Your Quick Reference)

Terms to know cold

• Par value: face amount repaid at maturity (typically $1,000)
• Coupon rate: annual interest rate, fixed at issuance
• Maturity: date when par value is returned
• Accrued interest: earned but unpaid interest between coupon dates

Key relationships to remember

• Price up → yield down (and vice versa)
• Current yield = annual coupon ÷ market price
• Clean price + accrued interest = what you actually pay
• Longer maturity = more price sensitivity to rate changes

Before you buy any bond

• Know the coupon rate, par value, and maturity date
• Check the current yield (not just the coupon rate)
• Ask about accrued interest so the settlement cost doesn't surprise you
• Understand whether you plan to hold to maturity or might sell early

Once these basics are solid, the next step is understanding how prices and yields move together mathematically — covered in Bond Math Basics: Price/Yield Relationship. For learning how bonds are quoted in practice, see Reading Bond Quotes and Price Conventions.