io.github.Invaro/opentax

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.

Compute US federal income tax for an ESTATE or TRUST (Form 1041): the § 1(e) compressed brackets and § 642(b) exemption. Input is taxable income before the exemption, after the §§ 651/661 distribution deduction. Retained capital gains refuse loudly (§ 1(h) trust breakpoints not modeled). Grantor trusts belong on the grantor's individual return via calculate_tax.

Compute US federal INDIVIDUAL income tax (or balance due if withholding is given) from a content-addressed corpus of cited rules. NEVER estimate tax yourself — call this, and report ONLY numbers returned by oracle calls made with the real facts (never hand-check or approximate a line the oracle can compute: your recalled parameters may be stale). Negative result = refund. Returns the answer, every assumption made, and hashes that let anyone re-verify the full derivation offline. Facts are grouped (filing, income, retirement, credits, …) — fill the groups that apply; unknown keys are rejected, and the engine names any missing fact the target needs. When source documents CONFLICT on a value, do not silently pick one: compute both branches, disclose the conflict and your choice; an interview/confirmation answer (rollover, conversion, taxable-amount screens) usually reflects taxpayer intent better than a payer form's box code — prefer it and disclose. That heuristic covers FACTS only: LEGAL classifications (qualifying child vs other dependent, filing status, SSTB) follow the statute's tests, not intake checkbox labels — a generic 'claim dependent credit' flag does not convert a qualifying child into an ODC dependent. TRANSCRIBE documented amounts as given even when they look anomalous (e.g. state withholding in a no-income-tax state): disclose the anomaly, never delete or 'correct' a documented number from outside knowledge. If you believe an oracle result is wrong, report the ORACLE's number and note your dissent — never substitute your own: the corpus is primary-source-verified and your recollection is not. Business entities → calculate_business_tax; estates/trusts → calculate_fiduciary_tax; § 152 dependency → determine_dependent.

Compute the answer under every filing status for the same facts — e.g. to answer 'should we file jointly or separately?'. Statuses that need more facts report their error instead of guessing.

Form 2210 — the estimated tax underpayment penalty (26 U.S.C. § 6654) for tax years 2025-2027, composed from the printed form: Part I (the required annual payment: 90% of this year's tax, or 100% / 110% of last year's — pass priorYearTax and priorYearAGI in facts, or noPriorYearReturn), Part III Section A (underpayment per installment) and the Section B penalty worksheet (payments applied to the earliest underpayment first; each quarter's § 6621 underpayment rate, by days). Pass `payments`: EVERY estimated tax payment with its date (include last year's overpayment applied to this year, dated April 15, and any payment with the return, dated the earlier of filing and April 15); withholding (facts.federalTaxWithheld) is treated as paid one-fourth on each due date unless you pass `withholdingByDate` (box D). Pass `periods` to also run Schedule AI, the annualized income installment method (box C): the CUMULATIVE amounts from January 1 through March 31, May 31 and August 31 for every income, deduction and credit amount that is nonzero for the year (same fact ids as facts; the tool lists any it needs). Each Schedule AI column is the whole return computed on the period's amounts × 4, 2.4, 1.5 and 1, with the standard deduction in full, so every income type, deduction and credit the engine models is annualized; the columns refuse, with the reason, where the form doesn't settle the period treatment (foreign earned income exclusion, prior-year carryovers, premium tax credit, kiddie tax, household employment taxes, a dependent filer, the SALT cap binding in a period). The tool reports both methods and the lower penalty. A penalty that would run into a quarter whose rate the IRS hasn't announced is refused, with Section A still shown. Report the lines and notes verbatim.

Form 4562 — depreciation for an individual's businesses and rentals, tax years 2025-2027 (calendar year): § 179 expensing with the dollar limit, phase-out, married-filing-separately split, business income limitation and carryover; the § 168(k) special allowance (100% for property acquired after January 19, 2025; 40% in 2025 and 20% in 2026 for property acquired earlier; the TY2025 40% election; election out by class); MACRS with the printed Publication 946 tables (half-year, mid-quarter by the 40% test, mid-month for buildings; 150% DB, straight-line and ADS elections); dispositions during the year; listed property and the § 280F passenger automobile limits (2025 and 2026); and Rev. Proc. 87-56 asset classes for cost segregation (assetClass, e.g. '57.0', '00.11', '00.3'). Give EVERY asset in service: current-year assets with cost, placedInService and acquiredOn (the binding-contract date, which sets the bonus percentage); earlier assets also with convention (HY/MQ), section179Taken and specialAllowanceTaken. section179BusinessIncome is required when § 179 is elected or carried over (taxable income from actively conducted businesses including wages, without § 179, the half-SE-tax deduction or any NOL). Returns the form's lines, each asset's schedule, and the deduction by activity (Schedule C line 13, Schedule E line 18) — subtract each activity's amount from that business's income before depreciation. Situations the sources don't settle (short years, general asset accounts, 100% bonus on a passenger car, § 280F recapture, a disposition in the last recovery year) refuse with the reason. Report the lines and notes verbatim; dollars in, whole dollars out.

Compute the COMPLETE Form 1040 bottom-line set in one call — the lines that determine the return (1a, 9, 10, 11, 12e, 15, 16, 17 AMT, 19, 20, 22, 23, 24, 25d, 27a, 28, 32, 33, 34/37), each whole-dollar rounded by the engine, plus the modeled Schedule 3 credits (schedule3), in a loss year a losses block (Schedule 1 line 8a NOL deduction and 8p § 461(l) excess business loss, the Form 172 NOL and next year's pre-2018 and post-2017 NOL carryovers), when energy_credits inputs are given, the printed Form 5695 line set (forms['5695']), with passive_activities the Form 8582 lines (forms['8582']: Part I, the special allowance, line 11, and each activity's Schedule E/C/F result and unallowed loss to carry forward), with business property sales, installment sales or like-kind exchanges Form 4797 (forms['4797']: the net § 1231 amount, the lookback, the Schedule D line 11 and Schedule 1 line 4 amounts, unrecaptured § 1250 gain and each property's gain, recapture and § 1231 part; line numbers follow the year's form, renumbered in 2026), Form 6252 (forms['6252']: each sale's recapture, gross profit, contract price, installment income and unrecaptured § 1250 gain) and Form 8824 (forms['8824']: each exchange's realized, recognized and deferred gain, recapture and basis of the property received), and with business credits Form 8582-CR (forms['8582-CR']: the tax on net passive income, the special allowances, each activity's allowed and carried credit) and Form 3800 (forms['3800']: the § 38(c) limit, the credit allowed on Schedule 3 line 6a and the unused credit). Takes the SAME input as calculate_tax (prefer the documents block: transcribe W-2/1099-R/SSA-1099 boxes and dependent birth dates — SSA-1099s are first-class, box 5 and box 6 are summed for you; the tool derives ages, classifications, Part IV withholding, and penalties deterministically). Never assemble return lines by hand — this tool is the return. TRANSCRIPTION CONVENTIONS: (1) a PRIOR-YEAR Form 1040 in the file supplies CONTINUING conditions the current-year interview omits — the 'Someone can claim: You as a dependent' checkbox and the blindness boxes carry forward unless the current-year data contradicts them; (2) COMMUNITY PROPERTY: do NOT split income 50/50 between MFS spouses when they lived apart all year with no transfers (§ 66(a) allocates earned income to the earner) or when a written separation agreement ended the community — transcribe each document to its named earner; never invent a Form 8958 split the intake does not request; (3) bonus depreciation for assets placed in service 1/1-1/19/2025 is 40% (§ 168(k) pre-OBBBA phase-down; 100% only for property ACQUIRED after 1/19/2025).

Compose a STATE return's printed-form line set deterministically (2025 IL-1040 / VA 760 / CA 540 / NY IT-201 / PA-40 / NJ-1040 / OH IT 1040 / NC D-400 / GA 500 / MD 502 / MO-1040 / WI Form 1 / MN M1 / SC1040 / AL Form 40 / OR-40 / OK Form 511 / CT-1040 / KS K-40 / AR AR1000F / NM PIT-1 / NE 1040N / ID Form 40 / WV IT-140 / ME 1040ME / HI N-11, RI-1040, MT Form 2, DE PIT-RES, ND-1, VT IN-111) — correct line NUMBERS from the printed forms and whole-dollar rounding, with the state tax computed by the oracle targets internally. DE filing status 4 (married filing combined separate) is TWO returns on one form: pass filingStatus 'mfs' with deCombinedSeparate plus the deSpouse* column-A inputs, and each column gets its own $3,250 deduction and its own bracket climb. MT starts from FEDERAL TAXABLE INCOME and has no standard deduction, personal exemption or Social Security subtraction of its own, so mtFederalDeductions (federal Form 1040 lines 12e and 13b) is REQUIRED and the composer refuses without it; long-term capital gains are taxed separately at 3%/4.1% on the page 2 worksheet. NC and GA start from federalAGI: NC runs the AGI-tiered child deduction, the independent itemize-vs-standard selection, and the Bailey/military/SS auto-subtractions; GA FORCES itemizing for federal itemizers (pass gaFederalItemized), runs the per-spouse retirement exclusion and Low Income Credit targets, and caps total credits at the line 16 tax. PA is CLASS-BASED and NJ is CATEGORY-BASED: transcribe the pa*/nj* class-or-category fields (PA: Box 16 compensation, per-spouse loss classes; NJ: the line 15-26 category nets — a category loss is suppressed per the printed rule, and the composer runs the pension-exclusion, Worksheet H deduction-vs-credit, EITC/CTC/CDCC targets itself) — federalAGI is NOT the PA or NJ base. OH starts from federal AGI: pass federalAGI + ohBusinessIncome and the composer runs the Business Income Deduction, MAGI-tiered exemptions, and the Schedule of Credits ordering (retirement/senior/CDCC/exemption credits before the joint filing credit's line-11 base). Workflow: run compute_return first for the federal substrate, compute any state-specific components the citations describe (additions, subtractions, credits without targets — disclose each), then call this ONCE and report its line set VERBATIM. Never hand-assemble state line numbers: transposed lines on correct dollars are the dominant state error mode. ALWAYS pass taxableSocialSecurity and unemploymentCompensation when nonzero (VA/CA/NY subtractions are applied by the composer). For CA (TY2025 and TY2026), pass dependents and ageOrBlindBoxes (line 32 exemption credits, run through the AGI Limitation Worksheet on federal AGI) and caRentedPrincipalResidence (the line 46 renter's credit, tested on California AGI line 17); line 62 BHST is computed. CalEITC and YCTC are oracle targets passed as caCalEITC/caYCTC — us.ca.caleitc refuses for TY2026 until FTB prints the 2026 EITC Table. ALWAYS transcribe the intake's state-specific block (e.g. ca_tax_return.ca_form540_schca: AB 5 employee-classification additions; va_sch_a fields; county/use-tax questions) — those fields drive composer inputs. For VA MFJ, pass vaYourVagi/vaSpouseVagi (the separate-VAGI worksheet) so the composer can run the Spouse Tax Adjustment worksheet itself. For MD, pass mdSubdivision (the mandatory county tax — line 28), mdEicQualifyingChild for the 50%/100%/45% EIC routing, and mdNetCapitalGainSubject from an agent-completed Form 502CG when FAGI exceeds $350,000; the composer runs the pension-exclusion, exemption-chart, CTC, poverty-credit, and local EIC/poverty worksheets itself. Maryland part-year returns (Form 502 line 12 proration) are not composed. For MO, split each income item per spouse (moFagiYou/moFagiSpouse etc. — Missouri combined returns compute a SEPARATE chart tax per spouse), pass the line 9/10 federal-tax amounts per the printed lists, and remember the NEW TY2025 100% capital-gains subtraction (moCapitalGainYou/Spouse); Kansas City/St. Louis 1% earnings taxes are separate city returns the composer does not produce. For WI, pass wiScheduleIAdjustments (IRC frozen at 12/31/2022 — post-2022 federal changes convert on Schedule I), wiCapitalGainSubtraction from Schedule WD (30%/60% LTCG exclusion), and note the Act 15 SB-16 retirement subtraction FORFEITS every credit — the composer enforces the forfeiture; compute both ways before electing it. For MN, remember the IRC is frozen at May 1, 2023 (2025 OBBBA items convert on Schedule M1NC → mnAdditions/mnSubtractions), pass mnSsAlternativeMethod when AGI exceeds the SS threshold (the composer takes the greater), mnAmt whenever M1MT preferences exist, and mnNetInvestmentIncome for the 1% NIIT; M1C/M1REF credit schedules are transcribed buckets. For SC, the base is FEDERAL TAXABLE INCOME — pass scFederalTaxableIncome (Form 1040 line 15 verbatim; a negative amount is preserved via subtraction line r), NOT federalAGI; pass scNetLtcgAfterLosses for the 44% LTCG deduction (net LT gains against ALL capital losses first), the per-person retirement/military/age-65 fields (military retirement is 100% deductible and REDUCES the same person's other two deductions — the composer handles the interplay), and federalEITC (the composer adds the 125% NONREFUNDABLE SC EITC into line 13 itself — never also put it in nonrefundableCredits); the 2025 state-tax addback for federal itemizers goes in scAdditions. For AL, the composer builds Alabama AGI from transcribed lines (alWages = W-2 Box 16, alOtherIncome, alTaxableRetirement* for the Schedule RS 65+ $6,000 exclusion — still $6,000 in 2026, HB388 died) — federalAGI is NOT the base; pass alFederalTaxPlusNiit (1040 line 22 + Form 8960) and alFederalRefundableCredits (EIC+ACTC+AOC+adoption+2439) for the UNLIMITED line 12 federal tax deduction, and remember overtime earned Jan-Jun 2025 is exempt and already out of Box 16. For OR, pass the federal-tax-worksheet components (orFederal1040Line22, orFederalPtc from 8962 line 24, orFederalAoc/orFederalRefundableAdoption — the EITC/ACTC are NOT subtracted) for the AGI-capped line 10 subtraction, taxableSocialSecurity (subtracted in full), or2024TaxLiability for the 9.863% kicker, and the Kids Credit inputs (orKidsUnder6 + addbacks); OBBBA tips/overtime/vehicle-interest are CLAIMED for Oregon via OR-ASC codes 390/391/392 in orSubtractions but added back for the Kids Credit test. For OK, pass federalAGI (line 1) plus the Schedule 511-A pieces (taxableSocialSecurity is subtracted in FULL automatically; okMilitaryRetirement/okCsrsRetirement/okRailroadRetirement are 100% subtractions; okGovRetirement*/okOtherRetirement* run the per-person $10,000 exclusion), okOutOfStateIncome (triggers the Schedule 511-E proration of deductions and exemptions), okFederalItemized + the Schedule 511-D inputs (federal itemizers MUST itemize for Oklahoma; $17,000 cap excludes medical/charity), exemptions + okSpecialExemptions65 (the 65+ exemption has FAGI limits), okFederalChildCareCredit/okFederalChildTaxCredit (greater of 20%/5%, $100,000 FAGI cliff), the Form 538-S inputs (okStrEligible attested, okGrossHouseholdIncome = ALL household income incl. nontaxable), and the Form 511-EIC inputs (okEicEligible attested under 2020 rules; okEicEarnedIncome2025 and, optionally, okEicEarnedIncome2024 + okEicAgi2024 — the composer computes both years from the printed 2020 table and keeps the larger, then 5%). Remember the joint 4.75% bracket starts at $14,400, not the $12,200 surveys print. For CT, the whole tax is a schedule on CONNECTICUT AGI (exemption, rates, 2% add-back, recapture, credit percentage — Tables A-E) computed by us.ct.income_tax from line 5; pass federalAGI plus the Schedule 1 pieces (taxableSocialSecurity with ctSsTotalBenefits/ctSsProvisionalExcess for the line 41 worksheet; ctPensionAnnuityIncome/ctIraDistributions for line 48b; ctMilitaryRetirement, ctTeachersRetirement, ctChetContributions), the Schedule 3 property tax inputs (ctPropertyTaxResidence/ctPropertyTaxAuto1/ctPropertyTaxAuto2 — the composer caps at $300, phases out by CT AGI, and limits to line 10), Schedule 2 other-jurisdiction inputs, and federalEITC + ctEitcQualifyingChild (40% + $250, refundable). QSS uses the MFJ column everywhere. For KS, a federal QSS files as Kansas HEAD OF HOUSEHOLD (single-column rates, $6,180 deduction, $9,160 + $2,320 exemption); pass federalAGI, taxableSocialSecurity (subtracted 100%), ksExemptRetirement (KPERS/federal/military retirement, Schedule S A14), the Schedule A components (Kansas lets the filer itemize independently of the federal election — the composer takes the larger of standard and itemized), dependents + ksChildrenBornThisYear/ksStillbirths/ksDisabledVeterans, federalEITC (17%: nonrefundable to line 16, remainder refundable on line 22), and ksFederalChildCareCredit (50%). For NM, pass nmFederalDeduction (Form 1040 line 12 — REQUIRED; New Mexico subtracts the FEDERAL standard or itemized deduction), nmFederalItemized plus the Schedule A 5a/5d/5e and nmFederalStandardDeduction inputs for the line 10 add-back, dependents (line 5 exemptions and the $4,000 HOH/MFJ dependents deduction), taxableSocialSecurity (exempt under an AGI cliff), nmAge65OrBlindPersons / nmAge65Count / nmBlindCount, and nmModifiedGrossIncome (ALL household income, taxable or not) for the PIT-RC rebates; a federal QSS uses the joint column but gets no dependents deduction. For NE, pass dependents (federal CTC/ODC dependents → $171 exemption credits), ageOrBlindBoxes (line 2a), taxableSocialSecurity and neMilitaryRetirement (both 100% excluded), neFederalItemized + neFederalItemizedDeductions + neSaltIncomeTaxes for a federal itemizer, neFederalTaxBeforeCredits (1040 line 16 + Schedule 2 lines 2 and 8 — the § 77-2715(1) cap when net Schedule I adjustments are under $5,000), federalEITC (10%), and the Form 2441N inputs when AGI is $29,000 or less; a federal QSS uses the joint column. For ID, pass dependents and idQualifyingChildren (the $205 child tax credit sunsets after TY2025), ageOrBlindBoxes (line 12), idFederalItemized + idFederalItemizedDeductions + Schedule A lines 5a/5b/5c/5e for a federal itemizer (Idaho removes income OR sales taxes), taxableSocialSecurity (100% subtracted), the Form 39R retirement inputs (idRetirementEligible, gross SS and railroad benefits, qualifying benefits), idRequiredToFile=false when below the filing threshold (no $10 permanent building fund tax), and stateWithholding; the $155 Food Tax Credit per household member is automatic unless idDonateFoodCredit; a federal HOH or QSS uses the $9,622 joint threshold. For WV, pass dependents (exemptions × $2,000; no standard or itemized deduction), taxableSocialSecurity (100% exempt at federal AGI ≤ $100,000 MFJ / $50,000 others, else 65% in 2025), wvSpouseTaxableSocialSecurity and the spouse-column retirement inputs on a joint return, wvTaxpayerAge65OrDisabled / wvSpouseAge65OrDisabled for the $8,000 modification, wvEarnedIncome when federal AGI is $10,000 or less (low-income exclusion), wvFederalChildCareCredit (50%), the Schedule E, SCTC-A, HEPTC-1, and property-tax-adjustment inputs as applicable, and stateWithholding; a federal QSS files as 'Widow(er) with dependent child' on Rate Schedule I; the Family Tax Credit is automatic from federal AGI and family size. For ME, pass dependents (line 13a) and meDependentsUnderSix (the $305 / $610 refundable dependent credit), ageOrBlindBoxes (lines 12a-12d), taxableSocialSecurity (100% subtracted) plus meSocialSecurityReceived and the pension inputs for the $48,216 pension deduction, meFederalItemized + Schedule 2 amounts for a federal itemizer, meTotalIncome + mePropertyTaxPaid / meRentPaid for the Property Tax Fairness Credit (the Sales Tax Fairness Credit is automatic from total income), federalEITC + meHasQualifyingChild, and stateWithholding; Maine conforms to the IRC as of 12/31/2024 so the 2025 standard deduction is $15,000 / $30,000 / $22,500; a federal QSS uses the joint column and threshold. For HI, pass federalAGI (line 7) plus hiPensionExclusion (employer-funded pensions are exempt), taxableSocialSecurity (100% subtracted), hiReservePay, dependents and hiTaxpayerAge65/hiSpouseAge65 (each 65+ oval is one more $1,144 exemption; hiDisabledPersons for the $7,000 in-lieu exemption), the Worksheets A-1 to A-6 amounts for an itemizer (no SALT cap, but hiStateLocalIncomeTaxes needs federal AGI under $100,000 / $150,000 / $200,000; the § 68 limitation applies over $166,800), hiNetCapitalGain + hiNetLongTermCapitalGain for the 7.25% alternative tax, hiPresentOverNineMonths (REQUIRED attestation for the food/excise and renters credits) with hiRentPaid, hiChildCareExpenses + hiEarnedIncome (+ hiSpouseEarnedIncome) for the Schedule X credit, federalEITC (40%, refundable), hiOtherStateTaxEligible + hiOutOfStateIncome for the other-state credit, and stateWithholding; the standard deduction is $4,400 / $8,800 / $6,424 for 2025 (dependent filers: greater of $500 or hiEarnedIncome); a federal QSS uses Schedule II. For ND, the base is FEDERAL TAXABLE INCOME (Form 1040 line 15) — pass ndFederalTaxableIncome, which is REQUIRED and which the composer refuses without; it may be NEGATIVE (the booklet directs the filer to enter the negative number on line 1b even though Form 1040 line 15 shows 0), and federalAGI is line 1a only, feeding NOTHING. There is no North Dakota standard deduction and no personal exemption. The first bracket is ZERO PERCENT (0.00% / 1.95% / 2.50%), so a great many returns owe nothing at all; below $100,000 the $50 Tax Table is MANDATORY under section 57-38-30.3(10) and prices the row MIDPOINT, which the composer applies for TY2025 (set ndUseRateSchedule only to see the schedule's figure). Pass taxableSocialSecurity (excluded IN FULL, no cap or age test), ndMilitaryPay and ndMilitaryRetirement (both excluded in full), ndRailroadRetirementBenefits (line 8 — a filer holding both an SSA-1099 and an RRB-1099 splits federal line 6b between lines 8 and 15 by gross benefits), ndNetLongTermCapitalGain with ndCapitalGainAlreadyExcluded for the 40% exclusion and ndQualifiedDividends for the parallel 40%, ndCollegeSaveContributions ($5,000, doubled ONLY on a joint return), and ndLowerQualifiedIncome for the marriage penalty credit (joint returns only; the composer runs the whole worksheet, including the preprinted $15,750). QSS uses the joint COLUMN of the table and the joint rate schedule but is NOT a joint return — its College SAVE cap stays $5,000 and it gets no marriage penalty credit. Every North Dakota credit is NONREFUNDABLE. Schedule ND-1NR (part-year and nonresident) and Schedule ND-1FA farm income averaging are not composed. For VT, pass federalAGI (line 1) and the Schedule IN-112 pieces: taxableSocialSecurity with vtRetirementElection ('social_security' OR 'contributory_system' with vtContributorySystemIncome — the filer may elect only ONE, excluded in full at federal AGI up to $55,000 / $70,000 joint and phased out to $65,000 / $80,000), vtMilitaryRetirementIncome (a SEPARATE exclusion, full to $125,000 and phased out to $175,000, claimable in addition), vtNetAdjustedCapitalGain + vtEligibleLongTermGain + vtFederalTaxableIncome for the Schedule IN-153 exclusion (the greater of $5,000 and 40% of over-three-year gain, capped at 40% of federal taxable income), vtUsObligationInterest, vtFederalMedicalExpenses (only the excess over the Vermont deduction plus exemptions is subtracted), ageOrBlindBoxes ($1,250 each on line 4), dependents (line 5c), vtCharitableContributions (5%, max $1,000, itemizing not required), vtOtherStateIncome + vtOtherStateTaxPaid (Schedule IN-117), and the refundable Schedule IN-112 Part II inputs — federalEITC with vtEitcQualifyingChildren (38% with children, 100% WITHOUT), vtChildrenSixOrUnder ($1,000 each, phased out $20 per $1,000 of AGI over $125,000), vtFederalChildCareCredit (72%), vtVeteranDischargeRecord ($250 to $30,000 of AGI). Vermont has NO itemized deduction; below $75,000 the Tax Table is mandatory and the composer applies it; above $150,000 of federal AGI the tax is at least 3% of AGI less U.S. obligation interest. A federal QSS takes the joint deduction and column but no spouse exemption. The Renter Credit (RCC-146) and Property Tax Credit (HS-122) are separate claims, not composed; TY2026 refuses at line 4 until the 2026 standard deduction publishes.

Determine whether ONE candidate person is the taxpayer's § 152 dependent — qualifying child or qualifying relative, including multiple-support agreements and the divorced-parents release — as a proof-backed yes/no with citations. Feed the result into calculate_tax's credits group (qualifyingChildren / otherDependents).

Get a tax rule in full: statutory citation with its verbatim excerpt, validity window, parameters, the formula and applicability guard (the rule IR — rules are data), the rules and facts it depends on, and its content hash. Use to quote and explain the actual law behind an answer. Pass asOf to see only the version in force on that date.

Find exact dollar amounts where one more cent of an input costs MORE than a cent of tax (marginal rate over 100%) — e.g. the EITC investment-income kill switch, CTC phase-out steps. Every probe is a real evaluation.

Determine whether a job is on the Treasury Tipped Occupation list (Treas. Reg. § 1.224-1, final Apr 2026) for the § 224 'no tax on tips' deduction. Fuzzy-matches the job name; returns the official listing (name, TTC code, category) or a definitive 'not listed'.

Discover every input the tax corpus understands: id, type, whether required, and its documented default. Call this if unsure what information to collect from the user.

Look up the current-law dollar amounts behind a question ('standard deduction', 'CTC phase-out threshold', 'tips deduction cap') with their statutory citations and validity windows. Use this to fact-check ANY tax number before stating it — your training data likely predates the OBBBA.

Full-text search over the encoded tax-law corpus ('kiddie tax', 'NIIT threshold', 'california renters credit'). Returns matching rules: id, title, statutory citation, effective window, and a verbatim excerpt of the law text. A hit means the engine computes this; zero hits means it is outside the corpus — say so rather than guessing. Follow up with explain_rule for a hit's full formula, or lookup_tax_parameter for its dollar amounts.

Fact-check a claimed dollar amount about tax law ('the 2026 MFJ standard deduction is $32,200', 'CTC is $2,000 per child') against the corpus. Returns verified / refuted (with the correct value and citation) / unknown. Never states a verdict it cannot ground.

Verify a claimed tax amount (yours, a user's, or another tool's) against the law. Returns verdict 'verified' or 'refuted' with the correct value. Use this as a self-check before presenting any tax number. Put asOf (and target, if any) INSIDE the facts object — e.g. facts: {..., "asOf": "2025-12-31"} — otherwise the claim is checked under today's law.