How Does OID Raise Your Bond’s Cost Basis Each Year? (w/Examples) + FAQs

This article reflects federal rules as of June 2026 and covers tax year 2025 (returns filed in 2026). State conformity varies and is addressed below. Tax law changes often — confirm current figures with IRS.gov before you file. This guide is educational and is not a substitute for advice from a licensed CPA or tax attorney for your specific situation.

Quick Answer

Original Issue Discount (OID) raises your bond’s cost basis by the exact dollar amount of OID you report as income each year. Because you pay tax on that accrued discount annually, the IRS lets you add it to your basis. This prevents the same income from being taxed twice when you sell or the bond matures.

What This Really Means for Your Money

When you buy a bond for less than its face value, that built-in discount is treated as interest you earn a little at a time. Each year, you report a slice of it as income on your return, even though you do not receive a cash payment. To keep that yearly income from being taxed again as a capital gain later, the tax code lets you increase your cost basis by the same amount you already reported. Your starting cost climbs each year until, at maturity, it usually equals the face value you collect.

This matters most at sale and at maturity, where a wrong basis turns into a real tax bill. The Securities Industry and Financial Markets Association reports the U.S. bond market topped $58 trillion in outstanding debt, and millions of these instruments carry OID. Get the basis bump wrong and you either overpay tax on phantom gains or underreport income and invite an IRS notice. The good news: the math follows a fixed, predictable pattern once you learn it.

Here is what you will learn:

📈 How the constant yield method turns a bond’s discount into a yearly income number and an equal basis bump
🧾 How to read Form 1099-OID box by box so you adjust basis correctly
💵 Three fully worked dollar examples — corporate, Treasury STRIPS, and a secondary-market bond
⚠️ The double-tax trap that makes investors overpay at maturity, and how to dodge it
🗺️ Whether your state follows the federal OID rules or taxes it differently

OID, Broken Down Into Its Core Parts

Original Issue Discount is the difference between a bond’s stated redemption price at maturity (usually its face value) and its issue price (what the first buyer paid when the bond was created). If a company sells a $10,000 bond for $8,000 at issue, the $2,000 gap is OID. The IRS treats that $2,000 as interest income spread across the life of the bond, not as a capital gain at the end.

The rule lives in Internal Revenue Code Section 1272, which requires holders to include a portion of OID in income each year they own the bond. You owe tax on this income even though no cash lands in your account until maturity. This is why people call OID phantom income — the tax bill is real, but the cash is not there yet.

To stop that yearly income from being double-counted, Section 1272(d)(2) increases your basis by each amount you include. Your basis is your investment’s cost for figuring gain or loss. So the same number does two jobs every year: it adds to your taxable income and it adds to your cost basis. The two always move together, which is the heart of how OID protects you from being taxed twice.

The Adjusted Issue Price

The adjusted issue price is the bond’s running value for tax purposes. It starts as the original issue price and grows each year by the OID added to income, as explained in Treasury Regulation 1.1275-1. Think of it as the bond’s “tax cost” climbing toward face value over time.

You need this number because each year’s OID is calculated from it, not from the face value. If you miss this, your yearly accruals drift off, and your final basis will be wrong. At maturity, the adjusted issue price should equal the face amount you collect, which is exactly why a correctly tracked bond produces little or no gain at the end.

The Constant Yield Method

The IRS requires the constant yield method to spread OID across the years, set out in Treasury Regulation 1.1272-1. The formula is simple: multiply the adjusted issue price at the start of the period by the bond’s yield to maturity, then subtract any cash coupon interest paid that period.

The consequence of using a flat, straight-line split instead is real: you would report too much OID early and too little late, which mismatches your income and your basis bumps. A common misconception is that OID is the same amount every year — it is not. Because the adjusted issue price rises, the OID accrual grows slightly each year, like compound interest working in reverse.

Which Situation Applies to You?

OID basis rules bend depending on what you own and when you bought it. Find your case below, then follow the matching example further down.

You bought a brand-new bond at original issue and held it. This is the cleanest case — your basis simply rises by each year’s reported OID until it reaches face value.
You bought an OID bond on the secondary market at a further discount. You now also face market discount rules under Section 1276, which can turn part of your gain into ordinary income.
You bought an OID bond for more than its adjusted issue price. You have acquisition premium, which reduces the OID you report each year and shows up in Box 6 of Form 1099-OID.
You own a tax-exempt municipal OID bond. The OID is tax-exempt interest, but it still raises your basis, which surprises many sellers.
You own a Treasury STRIPS or zero-coupon bond. There is no cash coupon at all, so every dollar of return is OID, and your basis climbs steadily to face value.

Worked Example 1: A Taxable Corporate OID Bond

Maria buys a newly issued corporate bond for $8,000 with a $10,000 face value, maturing in 5 years, no cash coupon, and a yield to maturity of 4.56%. Her $2,000 discount is OID. Each year she multiplies her adjusted issue price by 4.56% to find that year’s OID, reports it as income, and adds the same amount to her basis.

Tax Year and Starting Basis	OID Reported = New Basis
Year 1 — start $8,000.00	$364.80 income → basis $8,364.80
Year 2 — start $8,364.80	$381.43 income → basis $8,746.23
Year 3 — start $8,746.23	$398.83 income → basis $9,145.06
Year 4 — start $9,145.06	$417.01 income → basis $9,562.08
Year 5 — start $9,562.08	$436.03 income → basis $9,998.11

Over five years Maria reports about $1,998 of OID income, and her basis rises from $8,000 to roughly $10,000 — the face value she collects at maturity. Because her basis now matches her payout, she has essentially no taxable gain at maturity. The small rounding gap of about $2 reflects the figures on her Form 1099-OID, which she should follow over hand calculations.

Worked Example 2: A Treasury STRIPS Zero-Coupon Bond

Treasury STRIPS pay no interest until maturity, so 100% of the return is OID. James buys a STRIPS for $800 with a $1,000 face value and a 4.56% yield. He reports OID income and bumps his basis every year, the same way Maria does.

Tax Year and Starting Basis	OID Reported = New Basis
Year 1 — start $800.00	$36.48 income → basis $836.48
Year 2 — start $836.48	$38.14 income → basis $874.62
Year 3 — start $874.62	$39.88 income → basis $914.51

The key wrinkle for Treasury bonds is that OID on federal obligations is exempt from state and local income tax, even though it is fully federally taxable. James reports the OID income on his federal return through Schedule B and tracks his rising basis so that, at maturity, his $1,000 payout produces no surprise federal gain.

Worked Example 3: An OID Bond Bought at a Further Discount (Market Discount)

Now the messy real-world case. Priya buys an existing corporate OID bond on the secondary market. Its adjusted issue price on her purchase date is $8,500, but she pays only $8,000. That extra $500 gap below the adjusted issue price is market discount, governed by Section 1276.

Here is what changes. Priya still accrues and reports OID each year and bumps her basis by it, exactly like Maria. But the $500 market discount is separate: when she sells or the bond matures, gain up to the accrued market discount is taxed as ordinary income, not capital gain, under Section 1276(a). She can either report the market discount yearly (which raises basis too) or wait and report it all at disposition. Market discount accrues on a straight-line basis unless she elects the constant-yield method, per Section 1276(b).

Priya’s Move	Tax Consequence
Accrues OID yearly	Reports OID as income; basis rises by each accrual
Holds $500 market discount until sale	Up to the accrued portion is taxed as ordinary income, not capital gain
Elects to accrue market discount yearly	Reports it annually as interest; basis also rises by those amounts

How OID Shows Up on Form 1099-OID

Your broker reports OID on Form 1099-OID, usually issued by January 31. Reading it correctly is how you land the right basis. Each box has a job, and skipping one is how investors overpay or underreport.

Box 1 — Original issue discount. The taxable OID for the year on a non-Treasury bond. This is the amount that both hits your income and raises your basis.
Box 2 — Other periodic interest. Stated cash interest paid on the bond, reported separately as interest income.
Box 6 — Acquisition premium. If you paid more than the adjusted issue price, this amount reduces the OID you actually report, per the Form 1099-INT and 1099-OID instructions.
Box 8 — OID on U.S. Treasury obligations. Federally taxable but state-tax-exempt OID; track this separately for your state return.
Box 10 — Bond premium. Premium that offsets interest for bonds bought above face value.
Box 11 — Tax-exempt OID. OID on municipal bonds; not federally taxable, but it still increases your basis.

The acquisition premium in Box 6 is the most-missed entry. If you ignore it, you report too much OID income and overpay tax. Your actual taxable OID is Box 1 minus Box 6, never below zero, as IRS Publication 1212 explains.

Reporting the Sale: Form 8949 and Schedule D

When you sell or redeem the bond, you report it on Form 8949 and carry the totals to Schedule D. Your basis on Form 8949 must include every dollar of OID you reported over the years. Brokers often report an OID-adjusted basis on Form 1099-B, but not always — if it shows the original purchase price only, you must adjust it yourself using a Code B in column (f), per the Form 8949 instructions.

The consequence of skipping this is direct money lost. If your 1099-B shows your $8,000 purchase price but you reported $1,998 of OID over the years, your true basis is about $10,000. Report the lower number and you pay capital gains tax on a $2,000 “gain” that does not exist — tax you already paid year by year. This is the double-tax trap, and it is the single most expensive OID mistake.

Mistakes to Avoid

Forgetting to raise basis at all. You pay tax on phantom OID income every year, then pay capital gains tax again at sale on the same money.
Trusting an unadjusted 1099-B basis. Some brokers report only your purchase price; selling on that number creates a fake gain and an overpayment.
Ignoring Box 6 acquisition premium. Reporting full Box 1 without subtracting Box 6 overstates your income and inflates your tax bill.
Treating municipal OID as basis-neutral. Tax-exempt OID still raises basis; skipping it overstates your gain on a muni sale.
Using straight-line instead of constant yield. The IRS mandates the constant yield method; a flat split mismatches your income and basis each year.
Missing the market discount rules. Buying an OID bond below its adjusted issue price triggers ordinary-income treatment under Section 1276, not the lower capital-gains rate.
Skipping state adjustments on Treasury OID. Treasury OID is state-tax-exempt; reporting it as state income overpays your state tax.
Not reporting OID under $10. A broker need not issue a 1099-OID below $10, but you still owe tax and must self-report it.

Do’s and Don’ts

Do track your adjusted issue price every year, because each year’s OID is calculated from it, not the face value.
Do keep your broker statements and Publication 1212 OID tables, because they prove your basis if the IRS asks.
Do subtract Box 6 acquisition premium from Box 1, because that is your real taxable OID.
Do separate Treasury OID for your state return, because it is exempt from state income tax.
Do reconcile your 1099-B basis before you file, because a missing OID adjustment costs you real money.
Don’t assume OID is the same dollar amount each year, because the constant yield method makes it grow.
Don’t report a municipal OID sale at original cost, because the tax-exempt OID raised your basis.
Don’t ignore a market discount bond’s ordinary-income rule, because the higher rate applies to that gain.
Don’t rely on memory for multi-year accruals, because rounding errors compound over the bond’s life.
Don’t skip a professional for distressed or complex debt, because market discount and OID overlap can get costly fast.

Pros and Cons of OID Basis Adjustments

Pro: It prevents double taxation, because the income you already paid tax on becomes part of your cost.
Pro: It produces little or no gain at maturity, because basis climbs to meet the face value.
Pro: The math is predictable, because the constant yield method follows a fixed formula every year.
Pro: Brokers usually do the tracking, because 1099-OID and adjusted 1099-B reporting are now common.
Pro: It rewards careful records, because accurate basis tracking directly lowers your tax at sale.
Con: You owe tax on phantom income, because OID is taxed yearly before you receive cash.
Con: It adds recordkeeping, because you must follow the adjusted issue price across many years.
Con: Errors are easy and costly, because a single missed adjustment causes double taxation.
Con: Market discount overlap is confusing, because two separate accrual rules can apply at once.
Con: State treatment varies, because Treasury and muni OID follow different state rules than corporate OID.

Does Your State Follow the Federal OID Rules?

Start with the federal baseline: OID is taxable interest, and it raises your basis. Most states with an income tax follow the federal treatment for corporate OID because they begin from your federal adjusted gross income. That means the basis you build for federal purposes generally carries over to your state return.

Two big exceptions matter. First, OID on U.S. Treasury obligations (Box 8) is exempt from state and local income tax under 31 U.S.C. 3124, so states like California and New York let you subtract it. Second, municipal bond OID (Box 11) is federally tax-exempt, and many states also exempt interest on their own bonds while taxing other states’ munis. States with no income tax — such as Texas, Florida, and Washington — do not tax any OID at all, though it still raises your federal basis. Always confirm with your state’s department of revenue, because conformity genuinely varies.

What to Do Next

Pull your Form 1099-OID and 1099-B for tax year 2025 as soon as your broker posts them, usually by late January 2026.
Confirm your taxable OID by subtracting Box 6 acquisition premium from Box 1, never going below zero.
Verify your 1099-B basis includes all OID you reported; if not, plan a Code B adjustment on Form 8949.
Separate Treasury OID (Box 8) so you can subtract it on your state return.
Gather your multi-year OID records and the relevant Publication 1212 tables to support your basis.
File by April 15, 2026, and call a CPA if you hold market discount bonds, distressed debt, or foreign OID, because those cross-rules get complex and a single error can cost hundreds in extra tax.

FAQs

Does OID increase my cost basis?

Yes. Under Section 1272(d)(2), your basis rises by each dollar of OID you include in income each year. This prevents the same amount from being taxed again as a capital gain at sale or maturity.

How much does my basis go up each year?

By the exact OID amount you report, found by multiplying your adjusted issue price by the yield to maturity and subtracting any cash coupon. For tax year 2025, that figure usually appears in Box 1 of your Form 1099-OID.

Is OID taxed even if I receive no cash?

Yes. OID is “phantom income” — you owe federal tax on the accrued amount each year even though most bonds pay nothing until maturity. This applies to zero-coupon and Treasury STRIPS bonds in particular.

What is the de minimis OID rule?

OID is treated as zero if it is under 0.25% of face value times the years to maturity, per Section 1273(a)(3). Below that small threshold, you skip annual accrual and treat the discount as a capital gain at sale.

Does municipal bond OID raise my basis?

Yes. Even though tax-exempt OID in Box 11 is not federally taxable, it still increases your cost basis. Many sellers miss this and overstate their gain when they sell a muni bond.

What is acquisition premium on a 1099-OID?

It is the amount you paid above the adjusted issue price, shown in Box 6. It reduces your taxable OID for the year, so your real OID income is Box 1 minus Box 6, not below zero.

How is OID different from market discount?

OID is built into a bond at issue; market discount arises when you buy it later below its adjusted issue price. OID is reported yearly as interest, while market discount under Section 1276 is often taxed as ordinary income at sale.

Which form reports OID income?

Form 1099-OID, issued by your broker, usually by January 31. You report the income on Schedule B and any sale on Form 8949 and Schedule D for the year you sell or redeem.

Is Treasury OID taxed by my state?

No. OID on U.S. Treasury obligations is exempt from state and local income tax under 31 U.S.C. 3124, though it remains fully taxable on your federal return.

What happens if I forget to raise my basis?

You pay tax twice on the same money. You already paid annual tax on the OID, then capital gains tax on a fake gain at sale. Fixing it may require an amended return on Form 1040-X.

Does OID apply to brokered CDs?

Yes, if a CD is issued at a discount and matures in more than one year, it can carry OID and gets a yearly basis bump like a bond. Short-term CDs maturing within a year follow different rules.

Where can I find the official OID amounts?

IRS Publication 1212 lists OID figures for many publicly offered instruments. You can download it from the IRS OID publication page to confirm your broker’s reported numbers.

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