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Form 6251

Also called: IRS Form 6251

In one line

The IRS form used to calculate whether you owe alternative minimum tax.

In plain English

Form 6251 is where AMT is actually computed. Exercising ISOs is a common reason it kicks in, because the bargain element is added back here.

If you were explaining it to a 5-year-old

It's the special worksheet the taxman uses to check if the backup tax rule applies to you this year.

Why it matters when you sell

If you exercise ISOs, Form 6251 is where your potential AMT surprise shows up — worth modelling before, not after, you exercise.

Related terms

Alternative minimum tax (AMT)Incentive stock option (ISO)Bargain elementForm 3921

Put it to use

Cost to exercise + AMT

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Sources

Primary references for this term: IRS (US tax). Our definitions are written in plain English and kept evergreen — see the glossary methodology. General information, not advice.

Educational information only — not financial, tax or legal advice, and not an offer to buy or sell any security. Definitions are general; your own documents and local law govern your situation. PrivateTechShares is independent and not a broker or marketplace.