tools · POST /v1/tools/calculate_business_tax

calculate_business_tax

Form 1120 taxable income and tax, S-corp entity taxes, classification, estimates. Calculation only.

Call it

bash

curl -s https://opentax.invaro.ai/v1/tools/calculate_business_tax \
  -H "Authorization: Bearer $OPENTAX_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "entityLegalForm": "corporation",
  "corpTaxableIncome": 1000000,
  "asOf": "2025-12-31"
}'

What it does

Compute US federal BUSINESS-ENTITY tax from the same cited corpus: check-the-box entity classification, Form 1120 corporate income tax (§ 179/168(k)/174A/163(j)/DRD/NOL, § 250, GBC/FTC/BEAT), S-corp entity taxes, corporate estimates, the § 4501 buyback excise, AET and PHC taxes. Individual returns → calculate_tax. Unknown keys are rejected; unmodeled territory refuses loudly with the reason.

This is the description the MCP server hands to a model. The imperative sentences are addressed to the model; the facts about scope apply to every caller.

Inputs

Nothing is syntactically required, but computation needs asOf, and the engine names any fact the target depends on with NEEDS_FACTS.

field	type	description
corpIsREITorRIC	boolean	The corporation is a real estate investment trust (§ 856) or regulated investment company (§ 851). REFUSES — their dividends-paid deduction and distribution requirements are not modeled.
employeeAnnualWages	number \| string	One employee's annual wages, for the employer-side payroll-tax target (§ 3111 FICA + FUTA). In dollars.
qreCurrentYear	number \| string	Qualified research expenses for the current year (§ 41(b); § 41(d) qualification attested). In dollars.
qreAvgPrior3Years	number \| string	Average annual qualified research expenses over the 3 preceding years — 0 means no prior QREs (the 6% startup rate of § 41(c)(4)(B) applies). In dollars.
entityLegalForm	"llc" \| "corporation"	The business's state-law legal form: a limited liability company, or a state-law corporation (a per-se corporation under Treas. Reg. § 301.7701-2(b)(1)).
llcMemberCount	integer \| string	Number of members (owners) of the LLC — one member defaults to disregarded-entity treatment, two or more to partnership (Treas. Reg. § 301.7701-3(b)(1)).
filedForm8832CorpElection	boolean	The entity filed a Form 8832 election to be classified as an association taxable as a corporation (Treas. Reg. § 301.7701-3(c)).
filedForm2553SElection	boolean	The entity filed a timely Form 2553 S election under § 1362(a)(1) (for an eligible entity this also deems association classification, Reg. § 301.7701-3(c)(1)(v)(C)).
sCorpShareholderCount	integer \| string	Number of shareholders, counting married couples and § 1361(c)(1) family members as one (§ 1361(b)(1)(A): may not exceed 100).
sCorpHasIneligibleShareholder	boolean	Any shareholder is ineligible under § 1361(b)(1)(B)–(C): a nonresident alien, or an entity other than an estate or eligible trust/exempt organization.
sCorpHasMultipleStockClasses	boolean	The corporation has more than one class of stock (§ 1361(b)(1)(D); differences in voting rights alone do not create a second class, § 1361(c)(4)).
corpTaxableIncome	number \| string	The C corporation's taxable income BEFORE the § 250 deduction, if already computed — used as-is when provided. Leave at 0 to have the engine compute it from corpGrossIncome and the deduction components (charitable/DRD/NOL machinery). CONTRACT: the § 250 deduction is computed separately from corpFDDEI/corpNCTI and subtracted by the tax rule — an AS-FILED Form 1120 line 30 already nets out § 250, so when providing corpFDDEI/corpNCTI enter the pre-§ 250 amount here (line 30 plus the § 250 deduction as filed), never the net. In dollars.
corpGrossIncome	number \| string	The corporation's gross income (§ 61), INCLUDING any dividends received, any § 951 subpart F and § 951A NCTI/GILTI inclusions with their § 78 gross-ups (§ 951A(a) is a gross-income INCLUSION — the § 250 deduction is computed separately from corpNCTI), and any § 245A-eligible foreign-sub dividends. In dollars.
corpOrdinaryDeductions	number \| string	Ordinary business deductions (salaries, rents, prior-year amortization, …) — everything EXCEPT charitable contributions, the dividends-received deduction, and NOLs, which have their own limited rules. Enter compensation already limited by § 162(m) (no deduction for a covered employee's remuneration over $1,000,000 at a publicly held corporation — not modeled, attested). In dollars.
corpCharitableContributions	number \| string	The corporation's charitable contributions — current-year gifts plus allowable prior-year § 170(d)(2) carryovers being used (both subject to the same ceiling and, from 2026, the OBBBA floor). In dollars.
corpDividendsReceived	number \| string	Dividends received from other taxable domestic corporations (§ 243 DRD; must also be included in corpGrossIncome). Enter only dividends on stock meeting the § 246(c) holding period (held more than 45 days during the 91-day window around the ex-dividend date; 90/181 for certain preferred) — attested; § 1059 extraordinary-dividend basis reduction not modeled. In dollars.
corpDrdOwnershipTier	"under-20" \| "20-to-80" \| "80-plus"	Ownership of the dividend-paying corporation: under 20% (50% DRD), 20–80% (65% DRD), or 80%+ affiliated (100% DRD, § 243(a)(3)).
corpNOLCarryforward	number \| string	Net operating loss carryforward available this year (§ 172: deduction limited to 80% of taxable income before the NOL; post-TCJA, no carrybacks). In dollars.
corpPriorYearTax	number \| string	Tax shown on the corporation's preceding-year return (§ 6655(d) prior-year prong; unavailable if that year showed zero tax or was short). In dollars.
corpIsLargeCorporation	boolean	The corporation had taxable income of $1,000,000 or more in any of the 3 preceding taxable years (§ 6655(g)(2) 'large corporation' — may not use the prior-year safe harbor).
corpFDDEI	number \| string	TY2025: foreign-derived intangible income (FDII); TY2026+: foreign-derived deduction eligible income (FDDEI, OBBBA — QBAI abolished). The § 250 deduction applies 37.5% (2025) / 33.34% (2026+). In dollars.
corpNCTI	number \| string	TY2025: the § 951A GILTI inclusion (with its § 78 gross-up); TY2026+: net CFC tested income (NCTI, OBBBA). The § 250 deduction applies 50% (2025) / 40% (2026+). The inclusion itself is GROSS INCOME (§ 951A(a)) — it must also be in corpGrossIncome with its § 78 gross-up; this fact drives only the § 250 deduction and FTC basket. The per-CFC tested-income aggregation is not modeled. In dollars.
generalBusinessCredits	number \| string	Aggregate current-year § 38(b) general business credits (e.g. the § 41 research credit target's result) — limited under § 38(c). In dollars.
corpForeignTaxesGeneral	number \| string	Creditable foreign income taxes in the § 904(d) GENERAL basket. In dollars.
corpForeignSourceIncomeGeneral	number \| string	Foreign-source taxable income in the general basket (§ 904 limitation numerator; § 861 expense allocation attested). In dollars.
corpForeignTaxesNCTI	number \| string	Foreign taxes attributable to the § 951A basket (GILTI/NCTI) — the § 960(d) deemed-paid credit takes the 80% (2025) / 90% (2026+, OBBBA) allowance, no carryovers. In dollars.
corpBaseErosionTestMet	boolean	The corporation's base erosion percentage is 3% or more (2% for banks/securities dealers) — one of the two § 59A applicable-taxpayer tests. BEAT applies only to $500M+ multinationals.
corpBaseErosionTaxBenefits	number \| string	Base erosion tax benefits for the year (§ 59A(c)(2)) — include the base-erosion percentage of any NOL deduction (§ 59A(c)(1)(B)). Added back to reach modified taxable income. In dollars.
corpCapitalGains	number \| string	The corporation's capital gains for the year (§ 1211(a): losses offset only these; net gain is ordinary-rate income for a corporation). In dollars.
corpCapitalLosses	number \| string	The corporation's capital losses for the year, including prior-year § 1212(a) carryovers being used (allowed only to the extent of capital gains). In dollars.
corpPortfolioDebtFinancedPercent	integer \| string	Average indebtedness percentage (0-100) of debt-financed portfolio stock (§ 246A) — reduces the 50%/65% DRD proportionally; 0 = not debt-financed.
corpFilesConsolidatedReturn	boolean	The corporation joins a consolidated return (§§ 1501-1504) — intercompany eliminations and SRLY rules are not modeled, so this refuses.
corpTIThrough3Months	number \| string	Corporate taxable income for the first 3 months (§ 6655(e) annualization, installments 1-2). In dollars.
corpTIThrough6Months	number \| string	Corporate taxable income for the first 6 months (§ 6655(e) annualization, installment 3). In dollars.
corpTIThrough9Months	number \| string	Corporate taxable income for the first 9 months (§ 6655(e) annualization, installment 4). In dollars.
sCorpHasAccumulatedEandP	boolean	The S corporation has accumulated earnings and profits from C-corporation years at the close of the year (§ 1375 applies only then).
sCorpPassiveInvestmentIncome	number \| string	The S corporation's passive investment income — royalties, rents, dividends, interest, annuities (§ 1375(b)(3)). In dollars.
sCorpGrossReceipts	number \| string	The S corporation's gross receipts for the year (§ 1375). In dollars.
sCorpNetPassiveIncome	number \| string	Passive investment income net of directly-connected deductions (§ 1375(b)(2)). In dollars.
sCorpTaxableIncomeAsC	number \| string	The S corporation's taxable income computed as if it were a C corporation (§§ 1374(b)(1)/1375(b)(1)(B) cap). In dollars.
sCorpRecognizedBuiltInGain	number \| string	Net recognized built-in gain during the § 1374(d)(7) 5-year recognition period after a C-to-S conversion (0 if the period has passed or there was no conversion). In dollars.
corpAvgAdjustedFinancialStatementIncome	number \| string	3-year-average adjusted financial statement income (§ 56A) — over $1 billion triggers the corporate AMT, which this engine refuses to approximate. In dollars.
corpEquipmentPurchases	number \| string	Cost of qualified § 168(k) property acquired AND placed in service this year (acquired after January 19, 2025 — 100% bonus depreciation, OBBBA-permanent). EXCLUDE passenger automobiles (the § 280F luxury-auto caps are not modeled) and anything entered in corpSection179Cost. In dollars.
corpSection179Cost	number \| string	Cost of § 179 property the corporation elects to expense — including qualified real property (roofs, HVAC, fire/security systems on nonresidential real property, § 179(d)(1)(B)(ii)) that § 168(k) cannot reach. Must NOT also be in corpEquipmentPurchases; EXCLUDE passenger automobiles and sport utility vehicles (the § 280F caps and the § 179(b)(5) SUV cap are not modeled). In dollars.
corpFiscalYearFiler	boolean	The corporation uses a FISCAL taxable year (or files a § 443 short-period return). Fiscal and short years are not modeled — the OBBBA parameters (§ 250 rates, § 59A 10.5%, § 960(d) 90%, § 448(c) $32M, the § 170(b)(2) 1% floor) apply by the taxable year's BEGINNING date, and § 443(b) annualization / § 15 proration are not encoded.
corpIsCoveredCorporation	boolean	The corporation is a 'covered corporation' for the § 4501 stock-repurchase excise tax: a domestic corporation whose stock is traded on an established securities market (§ 4501(b)).
corpStockRepurchasedFMV	number \| string	Fair market value of the corporation's own stock repurchased (§ 317(b) redemptions and economically similar transactions) during the taxable year, for the § 4501 excise. In dollars.
corpStockIssuedFMV	number \| string	Fair market value of stock issued by the corporation during the taxable year (including to employees) — netted against repurchases under § 4501(c)(3). In dollars.
corpSection245ADividends	number \| string	Foreign-source portion of dividends received from specified 10-percent-owned foreign corporations, eligible for the § 245A participation-exemption DRD (100%). Must also be included in corpGrossIncome. Attested by entry: US-shareholder status, NOT a § 245A(e) hybrid dividend, and the § 246(c)(5) 365-day holding period met; no foreign tax credit is allowed for the deducted portion (§ 245A(d)) — keep these taxes out of the FTC inputs. In dollars.
corpDomesticResearch	number \| string	Domestic research or experimental expenditures — currently deductible under § 174A (OBBBA, permanent from 2025). In dollars.
corpForeignResearch	number \| string	FOREIGN research or experimental expenditures paid this year — capitalized and amortized over 15 years (§ 174; first-year deduction is 1/30 under the midpoint convention). In dollars.
corpBusinessInterestExpense	number \| string	Business interest expense (§ 163(j): limited to 30% of EBITDA-based ATI unless the § 448(c) gross-receipts test is met). In dollars.
corpAvgGrossReceipts3yr	number \| string	3-year-average annual gross receipts (§ 448(c) test: $31M for 2025, $32M for 2026 — at or below it the § 163(j) limit does not apply). In dollars.
corpDividendsPaid	number \| string	Dividends paid during the year (the § 561 dividends-paid deduction for the accumulated-earnings computation). In dollars.
corpAccumulatedEandPStart	number \| string	Accumulated earnings and profits at the close of the PRECEDING year (§ 535(c)(2) minimum-credit offset). In dollars.
corpReasonableNeedsRetention	number \| string	Earnings retained for the reasonable needs of the business (§§ 535(c)(1), 537 — documented needs; part of the accumulated earnings credit). In dollars.
corpIsPersonalServiceCorp	boolean	The corporation's principal function is services in health, law, engineering, architecture, accounting, actuarial science, performing arts, or consulting (§ 535(c)(2)(B): $150,000 minimum credit instead of $250,000).
corpPHCIncome	number \| string	Personal holding company income (§ 543: dividends, interest, royalties, annuities, certain rents). In dollars.
corpAdjustedOrdinaryGrossIncome	number \| string	Adjusted ordinary gross income (§ 543(b)(2)) — the 60% test base. In dollars.
corpOwnedByFiveOrFewer	boolean	More than 50% of the stock's value was owned (directly or via § 544 attribution) by 5 or fewer individuals during the last half of the year (§ 542(a)(2)).
corpUndistributedPHCIncome	number \| string	Undistributed personal holding company income (§ 545: taxable income adjusted, less federal taxes and the dividends-paid deduction). In dollars.
target	string	rule to derive (default: us.federal.corp.entity_level_income_tax — the classification-aware entity income tax). Other targets: us.federal.corp.entity_classification, .taxable_income, .income_tax_after_credits, .beat, .estimated.quarterly_payment, .stock_buyback_excise, .accumulated_earnings_tax, .phc_tax, .s_corp_entity_taxes
asOf	string	REQUIRED for computation: the law-in-force date — use the intended tax year's year-end (e.g. "2025-12-31" for TY2025). Omitting it is an error, never a default. pattern ^\d{4}-\d{2}-\d{2}$
includeProof	boolean	include the full proof artifact in the response as `proof` (PROOF-FORMAT v2: every applied rule, input, assumption and rounding, verifiable offline against corpusMerkleRoot; ~200 KB). Default false — the hashes alone are returned.

Example

calculate business tax 1120. Captured from the engine at corpus build time.

argumentsjson

{
  "entityLegalForm": "corporation",
  "corpTaxableIncome": 1000000,
  "asOf": "2025-12-31"
}

responsejson

{
  "ok": true,
  "target": "us.federal.corp.entity_level_income_tax",
  "asOf": "2025-12-31",
  "answer": "$210,000.00",
  "valueCents": "21000000",
  "assumptions": [
    {
      "factId": "filedForm2553SElection",
      "value": {
        "type": "bool",
        "value": false
      },
      "source": "default",
      "rationale": "Assumed no S election absent contrary input"
    },
    {
      "factId": "corpAvgAdjustedFinancialStatementIncome",
      "value": {
        "type": "money",
        "value": "0"
      },
      "source": "default",
      "rationale": "Assumed 3-year-average AFSI at or below the $1 billion CAMT threshold absent contrary input"
    },
    {
      "factId": "corpIsREITorRIC",
      "value": {
        "type": "bool",
        "value": false
      },
      "source": "default",
      "rationale": "Assumed not a REIT/RIC absent contrary input"
    },
    {
      "factId": "corpFiscalYearFiler",
      "value": {
        "type": "bool",
        "value": false
      },
      "source": "default",
      "rationale": "Calendar taxable year assumed — fiscal-year and short-period returns refuse"
    },
    {
      "factId": "corpFilesConsolidatedReturn",
      "value": {
        "type": "bool",
        "value": false
      },
      "source": "default",
      "rationale": "Assumed a separate (non-consolidated) return absent contrary input"
    },
    {
      "factId": "corpFDDEI",
      "value": {
        "type": "money",
        "value": "0"
      },
      "source": "default",
      "rationale": "Assumed no foreign-derived eligible income absent contrary input"
    },
    {
      "factId": "corpNCTI",
      "value": {
        "type": "money",
        "value": "0"
      },
      "source": "default",
      "rationale": "Assumed no CFC inclusion absent contrary input"
    },
    {
      "factId": "corpBaseErosionTestMet",
      "value": {
        "type": "bool",
        "value": false
      },
      "source": "default",
      "rationale": "Assumed the 3% base-erosion test is not met absent contrary input (BEAT reaches only large multinationals with substantial related-party deductions)"
    }
  ],
  "corpusMerkleRoot": "sha256:5f34e0bc2fe5d80f540b75151cc8793bca4bda4555485dfb0d313927938f1911",
  "artifactHash": "sha256:c1db837ab77c46714d1733df3fc7ff3313ed5ba9b6a65af90dbde2c69e0f2e7d",
  "note": "Tell the user about any assumptions that may not match their situation. This is computation with citations, not tax advice."
}