1099-B Basis Missing or IRS Says Your Stock Basis Is Wrong

Being taxed on the entire sale price instead of actual gain.

The IRS treated my stock-sale proceeds as taxable gain because basis was missing. How do I fix it?

Gross proceeds are not the same as taxable gain: reconstruct adjusted basis, holding period, and transaction reporting, then respond through the procedure currently open.

Start with the procedural stage

Procedural stage: Information mismatch / basis

What happened: Broker reporting or IRS matching may show sale proceeds without the taxpayer’s basis, or basis reported by taxpayer differs from IRS/broker data.

Controlling deadline: CP2000/exam/deficiency deadline if a notice is open; otherwise amendment/refund limitation rules.

Right at risk: No single right applies; identify the procedural stage before stating the consequence.

Reconstruct the facts before choosing the response

What IRS knows / may use: Broker-reported gross proceeds, sometimes basis and covered/noncovered status, plus return Schedule D/Form 8949.

Taxpayer must reconstruct: Purchase confirmations, historical statements, reinvested dividends, corporate actions, inherited/gift basis facts, wash sales, adjustments, holding period, lot identification.

The rule and the response path

Technical rule: Gain/loss generally equals amount realized minus adjusted basis; information reporting does not eliminate the taxpayer’s burden to substantiate basis.

Primary authority: IRC §§1001, 1011–1016; Form 8949 and Schedule D instructions; Publication 550; IRS CP2000 guidance.

Forms / notices / letters: Form 1099-B, Form 8949, Schedule D, CP2000/exam notices.

Response options: Reconstruct lot-by-lot or transaction-level basis; reconcile broker data; provide clear schedule and source records; correct return if needed.

Payment, amendment, penalties and interest

When payment matters: Payment may stop or reduce further interest and some penalties once tax is assessed, but payment and procedural response are separate questions.

When payment does not resolve it: Payment does not cure a missed petition, appeal, substantiation, identity-verification, or information-response requirement unless the controlling procedure specifically says otherwise.

Amended return role: Do not default to Form 1040-X when an IRS notice, examination, math-error procedure, or other open process already controls the correction.

Penalty / interest distinction: Separate underlying tax, penalty, and interest. Relief from one does not automatically remove the others.

Common mistakes to avoid

• Treating the amount due as the procedural issue
• missing the deadline
• sending records without proof
• assuming an IRS data match establishes the substantive tax result

What can change the answer

Facts that change answer: Tax year; filing date; notice date; assessment status; prior IRS opportunities; payments; address; disputed item; pending examination or collection action.

Do not overstate: Do not assume missing broker basis means zero basis, and do not assume a taxpayer-created spreadsheet alone proves historical basis.

Professional help: High when basis is inherited/gifted, old brokerage data are missing, multiple corporate actions occurred, or disputed gain is material.

TAS role: Potentially relevant for qualifying hardship or system-failure cases, subject to TAS’s current case-acceptance limits.

State consequences: Check whether the federal change alters state taxable income, credits, filing obligations, or a state notice already in progress.

The PRISM principle

Gross proceeds are not the same as taxable gain: reconstruct adjusted basis, holding period, and transaction reporting, then respond through the procedure currently open.