| Adjustment | Grouping | Subgroup (residual only) | Amount (+ / −) |
|---|---|---|---|
How the IRS computes an imputed underpayment
Under the centralized audit regime the partnership pays the tax on audit adjustments in the adjustment year. IRC 6225(b)(1) defines the imputed underpayment as the result of “appropriately netting all partnership adjustments” for the reviewed year and “applying the highest rate of tax in effect for the reviewed year under section 1 or 11.” Treas. Reg. 301.6225-1(b)(1) breaks that into five steps, and the estimator follows them:
- Group the adjustments: reallocation, credit, creditable expenditure and residual groupings (Reg. 301.6225-1(c)). Most income and deduction changes fall in the residual grouping.
- Subgroup and net. Inside the residual grouping, adjustments net only if they would have been netted and allocated as a single item under IRC 702(a); a negative adjustment that could be limited if taken into account by a partner goes in its own subgroup. Give rows the same subgroup name to net them. In the reallocation grouping each positive and negative adjustment stands alone, because IRC 6225(b)(2) disregards the part of a reallocation that would decrease the imputed underpayment.
- Total netted partnership adjustment. Add the net positive subgroups. Net negative amounts are “adjustments that do not result in an imputed underpayment” and flow to the partnership's adjustment-year return under Reg. 301.6225-3.
- Multiply by the highest rate under IRC 1 or 11 for the reviewed year. The top rate in IRC 1(j) is 37% for tax years beginning after 2017; IRC 11(b) is 21%.
- Credits. Add net decreases in credits dollar for dollar. Net increases in credits reduce the amount only if the IRS decides to take them into account (Reg. 301.6225-1(e)(3)(ii)).
Modifications. The partnership can ask to reduce the amount under IRC 6225(c) on Form 8980: by the share allocable to tax-exempt partners, by adjustments partners take into account on amended returns or through the pull-in procedure, and by applying a lower rate to the share allocable to C corporations (or to individuals for capital gain and qualified dividends). The estimator applies whatever amounts you enter; the IRS decides what it approves. See modification requests. The alternative is a push-out election, which moves the adjustments to the reviewed-year partners instead.
Checked against the regulation's examples
The regulation's examples assume a 40% highest rate, which the test used. Example 3 ($200 ordinary income, $75 long-term gain, $50 less long-term loss, $30 less depreciation, all positive, and a $2 credit decrease) gives a total netted partnership adjustment of $355, $142 at 40%, and an imputed underpayment of $144, as the regulation states; the button above loads it. Example 4 (long-term gain recharacterized as $125 of ordinary income, entered as +125 in an "ordinary" subgroup and −125 in a "capital" subgroup) gives $50. Example 12 (reallocations of −30, +30, +70 and −70) gives a $100 total netted adjustment and $40. Example 1 (+5 ordinary income and −10 deduction in separate subgroups) gives $2; netted in the same subgroup as in Example 2 it gives zero.
Not modeled: specific imputed underpayments for particular partners, the recalculation when credits drive the result below zero (Reg. 301.6225-1(f)(3)), creditable foreign tax expenditure subgrouping, and interest. Interest on an imputed underpayment runs under IRC 6233 from the reviewed year's return due date. The imputed underpayment guide and the BBA overview cover the procedure.
Transition to Automatic Exemption from Penalty. The IRS First Time Abate page (reviewed October 2026) says FTA “is transitioning to a new relief called Automatic Exemption from Penalty (AEP), starting Summer 2026”. For Forms 1040, 1065 and 1120, Forms 940 through 945 and Form CT-1, beginning with 2025 tax year returns and 2026 quarterly returns, AEP is applied when the original return completes processing: with three prior years (or 12 consecutive quarters) of timely filing and payment, “The IRS won’t assess penalties for failure to file, failure to pay, or failure to make a deposit” and sends a letter saying the relief was applied; “You don’t need to contact the IRS or respond to the notice.” FTA continues to apply to earlier periods and to returns AEP does not cover, and the page says to contact the IRS if a penalty was assessed that should have qualified. See First Time Abate.
Questions practitioners ask
Why does a decrease in a deduction not offset an increase in income?
Because the regulations net adjustments only within a subgrouping, and a negative adjustment that could be limited if a partner took it into account (a deduction, a capital loss) goes in its own subgrouping unless it would have been netted with the income item on the return. Separate subgroups do not net, so the negative amount becomes an adjustment that does not result in an imputed underpayment.
What rate applies to a 2019 reviewed year?
The highest rate under IRC 1 or 11 for that year. For tax years beginning after 2017, IRC 1(j) sets the top individual rate at 37% and IRC 11(b) sets the corporate rate at 21%, so the imputed underpayment rate is 37% before modification.
Does the partnership pay penalties too?
Penalties and interest are figured at the partnership level and added to the imputed underpayment. The estimator shows the tax-equivalent amount only.
Can partners' amended returns reduce the imputed underpayment?
Yes. IRC 6225(c)(2) lets the imputed underpayment be determined without the adjustments that partners take into account on amended returns (or the pull-in alternative) and pay the tax on, if the IRS approves the modification.