Deterministic Indian income tax computation for a fiscal year. Handles new/old regime slabs, standard deduction, 87A rebate with marginal relief, 111A/112A capital gains rates, surcharge (with the 15% cap on gains), and 4% cess. All arithmetic is done in code from a versioned rule pack -- never estimated.

Compute tax under BOTH regimes for the same income and return a side-by-side comparison with the recommended regime and the savings amount. Pass the old-regime deductions you could actually claim; the new regime ignores them.

Build the advance tax installment plan (Jun 15 / Sep 15 / Dec 15 / Mar 15 at 15/45/75/100%) for an estimated tax liability net of TDS. Reports per-installment amounts and shortfalls against what has been paid so far.

Return the old-regime deduction checklist with statutory caps for a fiscal year (80C, 80CCD(1B), 80D tiers, 80TTA/TTB, 24(b), HRA metro list). Useful for estimating the deductions input to compute_tax/compare_regimes.

Parse the caret-delimited Form 26AS TEXT export from TRACES into structured TDS entries (deductor, TAN, section, amounts) with totals. Download the 'Text' format from TRACES -- it needs no password. PDF exports are not supported; the text export is more reliable.

Decrypt and parse the AIS JSON export from the income tax portal, entirely on-device. Provide pan + dob (DDMMYYYY) to derive the password, or pass it explicitly. Returns taxpayer info and normalized information rows (TDS entries, SFT transactions) with amounts, dates, and codes extracted by column label. The decryption scheme is reverse-engineered from the AIS utility; if it fails, use the portal's CSV export as a fallback and file an issue.

Deterministic sections 234B and 234C interest on advance-tax shortfalls. 234B: 1%/month on assessed-minus-advance when advance < 90% (from 1 April of the AY). 234C: per-installment shortfalls with the statutory 12%/36% safe harbors for June/September. Rule 119A rounding applied (principal floored to Rs 100, part month = full month).

HRA exemption per Rule 2A: least of (actual HRA, rent minus 10% of salary, 50% metro / 40% non-metro of salary), computed period-wise. Salary = basic + retirement-forming DA + fixed-percentage turnover commission. Old regime only; metro list for FY 2025-26 is Delhi/Mumbai/Kolkata/Chennai. Also computes the 80GG alternative for rent payers with no HRA.

Cross-document mismatch report -- the checks that pre-empt 143(1)(a) intimations and 139(9) defect notices: TDS claimed vs 26AS deposited (the ledger of record), missing-employer detection, AIS interest/dividend vs declared, Form 16 vs 26AS per-TAN totals. Pass whichever documents you have; checks needing missing inputs are reported as skipped.

Recommend ITR-1/2/3/4 for an individual from income heads, residency, losses, and disqualifier flags, with rule-by-rule reasoning. Loss-continuity aware: brought-forward business/speculative losses force ITR-3 even with zero current-year business income (Schedule CFL). Returns the filing deadline and 234F late fee for the recommended form.

Ordered, form-specific walkthrough for filing ITR-1/2/3/4 on incometax.gov.in: documents to gather, reconciliation, tax computation, portal steps schedule by schedule, and e-verification. Guidance only -- the taxpayer performs the final submit on the portal themselves.

List the fiscal years this server has rule packs for, with filing deadlines for the current assessment year.