U.S. · Tax forms
Form 6251 line 2c: investment interest.
How a second Form 4952 produces the AMT adjustment.
Line 2c is the difference between the investment interest you can deduct for the AMT and for regular tax. If you filled out Form 4952 for your regular tax, you fill out a second Form 4952 for the AMT, include interest that would have been deductible if private activity bond interest were taxable, and enter the difference between line 8 of the AMT form and line 8 of the regular tax form. If the AMT expense is greater, enter the difference as a negative amount.
Look up a step
Result
The four steps
| Item | Meaning | Where it goes (per the IRS instructions) |
|---|---|---|
| Step 1 | Form 4952 line 1 | Follow the Form 4952 line 1 instructions, but also include interest that would have been deductible if tax-exempt private activity bond interest were includible in gross income. |
| Step 2 | Lines 2 and 3 | Enter your AMT disallowed investment interest expense from 2024 on line 2. Complete line 3. |
| Step 3 | Part II | Refigure gross investment income, net gain and net capital gain from property held for investment, and investment expenses, taking all AMT adjustments and preferences into account. Include on line 4a private activity bond interest that goes on Form 6251 line 2g. On line 4g enter the smaller of regular line 4g or the total of AMT lines 4b and 4e. |
| Step 4 | Part III and line 2c | Complete Part III. Enter the difference between line 8 of the AMT Form 4952 and line 8 of the regular Form 4952 on Form 6251 line 2c; negative if the AMT expense is greater. |
| No itemizing | Investment interest not itemized | If you did not itemize and had investment interest, enter nothing on line 2c unless you reported it on Schedule E; then follow the steps and enter the difference between amounts allowed on Schedule E for regular tax and for AMT. |
Why the AMT figure differs
For the AMT, interest from private activity bonds that is tax-exempt for regular tax is added back on line 2g, which can increase the investment income that supports a deduction, and the AMT version of other items can differ too. The second Form 4952 lets you compare the two results line by line.
Worked example
Rhea itemizes and completed a regular Form 4952 with line 8 showing $4,000. Her AMT Form 4952, with the adjustments above, shows line 8 of $5,500. Her AMT expense is greater, so line 2c is entered as a negative $1,500, not as a positive adjustment. If the AMT line 8 had been $3,000, she would enter $1,000 as a positive amount.
Where to go next
The AMT only matters if the whole form produces tax; the AMT exemption calculator shows the exemption and phaseout side.
More IRS form line pages
Other pages in this set: Form 8949 Boxes A-L, Form 5329 Part III, Form 4562 Line 14, Form 4562 Line 12, Form 4562 Convention Codes, Form 5329 Line 52, Form 4562 Line 19, Form 4562 Line 42, Form 6251 Line 2i, Form 6251 Line 2l. The 1099-R box 7 lookup and W-2 box 12 lookup cover the same kind of question for those forms.
Sources
- Instructions for Form 6251 (2025): the sections for the lines and boxes on this page. Read November 2, 2026.
IRS page last reviewed April 30, 2026. Tax year 2025 edition. Line numbers, dollar limits and dates are those printed in the 2025 instructions and can change. Names in worked examples are made up.
Frequently asked questions
What is line 2c on Form 6251?
The AMT adjustment for investment interest: the difference between the amount allowed on a second AMT Form 4952 and the amount allowed on your regular tax Form 4952.
What sign do I use on line 2c?
Enter the difference between line 8 of the AMT Form 4952 and line 8 of the regular tax Form 4952. If your AMT expense is greater, enter the difference as a negative amount.
Do I need a second Form 4952?
Yes, if you filled out Form 4952 for regular tax. You complete a second one for the AMT and keep it with your records.
How do private activity bonds affect it?
Include interest that would have been deductible if the bond interest were taxable, and include the bond interest on line 4a, matching Form 6251 line 2g.
What if I do not itemize?
Do not enter anything on line 2c unless you reported investment interest on Schedule E; then use the Schedule E difference described in the instructions.
Not tax advice
This page summarizes IRS instructions, mostly written for the people who prepare the form, and is not tax, legal or financial advice. The payer, a CPA or an enrolled agent can confirm what a box or code means for your return. Everything runs in your browser; nothing you enter is sent anywhere.