# Fortax Advance Tax And Interest > Estimate current-year income, build the advance tax instalment schedule, compute interest u/s 234A, 234B and 234C with a script, tie every challan to 26AS, and prepare the e-Pay Tax challan (advance tax 100, self-assessment 300, regular assessment 400) for the CA to pay. Covers the 44AD/44ADA single instalment, resident senior citizens, and 234C relief for capital gains arising later in the year. Typical asks - "advance tax kitna bharna hai", "15 December ki installment", "234B 234C interest nikalo", "self assessment tax challan bana do", "challan 26AS me nahi dikh raha". - Skill: `amit-voais/fortax-advance-tax-and-interest` (Agent Skill, multi-file: 5 files) - Install (CLI): `npx skillmds@latest add amit-voais/fortax-advance-tax-and-interest` - Raw SKILL.md: https://api.skillmd.com/api/skills/amit-voais/fortax-advance-tax-and-interest/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - License: Apache-2.0 - Author: amit-voais (https://skillmd.com/u/amit-voais) - Updated: 2026-09-22 - Page: https://skillmd.com/skills/amit-voais/fortax-advance-tax-and-interest --- # Advance tax and interest under 234A, 234B and 234C Needs Python 3 and internet: runs `scripts/fortax.py` (the Fortax engine on ai.fortax.in; your file is processed and not stored). `scripts/compute_interest_234.py` runs locally (MIT, see `LICENSE-THIRD-PARTY-india-itr-copilot.txt`). ## Do the work, then stop at the payment The estimate, the instalment working, the interest computation, the challan tie-out and the filled e-Pay Tax screen are yours. **You never pay.** The CA presses Pay and completes the bank authentication. Refusing the working because the payment is theirs is a failure. Say where you will stop, then start. ## Step 0 — fix the year, and say which one you are in FY is April to March; AY = FY + 1. Advance tax is paid **during** the FY on that FY's income; self-assessment tax after it ends. Both carry the same AY on the challan and are told apart only by the minor head — get that wrong and the credit lands in the wrong bucket. State at the top of every working: the FY, the AY, the date you are computing as at, and whether the figures are estimated or actual. ## Step 1 — estimate the current-year income A forecast, and it must say so on its face. Build it from evidence, not from last year scaled up. | Head | Evidence | Trap | |---|---|---| | Salary | Payslips to date projected for the balance, the employer's TDS projection | Bonus, arrears, ESOP perquisite, mid-year job change | | House property | Rent agreement, interest certificate | Vacancy; a let-out treated as self-occupied | | Business or profession | Books to date, prior-year pattern, GST turnover as a cross-check | Year-end provisions, depreciation not yet booked | | Capital gains | Broker statements to date | A gain arising **after** an instalment date changes 234C — record each date | | Other sources | Interest accrued, dividend credited, AIS to date | Interest accrued but not yet credited | Take only deductions the assessee can substantiate today, not what they intend to invest by March; intentions go in the assumptions block, never into a figure. Compute under the regime that will actually apply and say which. Slabs, rebate, surcharge and cess come from a verified rules file for that year (the `fortax-itr` skill's `rules_AY.json`, or `python3 scripts/fortax.py kb "income tax slabs AY " --topics itr` with its source) — **never from memory and never from last year's working paper.** Use a spreadsheet with live formulas for the estimate. ## Step 2 — the instalment schedule The schedule is a sequence of cut-off dates in the FY, each with a cumulative percentage of the year's estimated liability. The structure is stable; **the dates and percentages are not yours to state from memory.** Look them up for that FY (`python3 scripts/fortax.py kb "advance tax due dates instalments" --topics itr`, or the portal) and record each in **Rules used** before computing. Under section 211 as it stood for recent years they were 15 June / 15 September / 15 December / 15 March at 15% / 45% / 75% / 100% — confirm for the year. Two variations rewrite the whole schedule and must be verified rather than assumed: - Assessees declaring presumptive income under 44AD(1) or 44ADA(1) pay the whole advance tax by 15 March in one instalment. This does not extend to 44AE. - A resident individual aged 60 or more with no business or profession income is outside advance tax (section 207(2)). Both are eligibility conditions — confirm each for that year and cite it. Build one row per instalment: cut-off date, cumulative percentage, cumulative tax required, paid to date, shortfall. The percentages apply to tax on estimated total income less the TDS and TCS genuinely expected — take that from 26AS plus what is realistic; an optimistic TDS assumption creates 234B. ## Step 3 — check what has been paid, against 26AS, not against the client Never compute a shortfall against what the client says they paid. Download 26AS for the AY (the `fortax-itr-portal-operations` skill, Step 4) and read the advance tax and self-assessment tax part. Record BSR code, challan serial, date of deposit, amount, minor head and AY for each, tie each to an instalment by its deposit date, then flag: - A challan in the folder but not in 26AS — not yet reported, or carrying the wrong PAN or AY. It is not paid until it appears. A challan in 26AS under the wrong AY or minor head needs a challan correction, not a second payment. Look up the current correction route and its time limit for that challan (portal service, bank or assessing officer) before advising. - A payment made after a cut-off — it counts from its actual date, not the date intended. ## Step 4 — the interest computations Compute each separately and show the workings. All three are simple interest on a base, for months, at a rate the Act fixes. **The rate, the rounding and the part-month convention are rules, not memory** — look each up and record it before multiplying. | Section | Charged for | Base | Period runs | |---|---|---|---| | 234A | Filing after the due date | Tax on total income less TDS/TCS, advance tax and reliefs (tax paid by the due date reduces it) | Day after the due date to the date of filing | | 234B | Advance tax paid is less than the required share of assessed tax (90% in recent years) | Assessed tax less advance tax paid | First day of the AY to assessment or payment, on the reducing balance | | 234C | Missing an instalment even where the year total is met | The shortfall at each cut-off | A fixed number of months per instalment | Verify per year: the threshold below which advance tax is not required at all (₹10,000 in recent years), the tolerances that excuse a 234C charge on the first two instalments (12% and 36% in recent years), and the relief where the shortfall comes from income that could not have been estimated at the earlier cut-off — capital gains, dividends, lottery, a first year of business — which applies only if the tax on it is paid in the remaining instalments or by 31 March. That is why Step 1 asked for the date of each gain. Run the script rather than multiplying by hand (individual assessees; for others use a spreadsheet with the same logic): ```bash python3 scripts/compute_interest_234.py --tax 150000 --tds 120000 --fy 2025-26 \ --pay-date 2026-07-30 --due-date 2026-07-31 --file-date 2026-07-30 \ --age 45 [--non-resident] [--has-business-income] [--presumptive 44AD|44ADA] \ --advance 2025-09-10:5000 2025-12-12:4000 \ --payment 2026-05-02:20000 \ --income-event 2025-11-20:30000 \ --total-income 1450000 --rate 0.01 --threshold 10000 ``` - `--tax` total liability including surcharge and cess; `--tds` TDS + TCS as in 26AS. - `--advance DATE:AMT` advance-tax challans up to 31 March; `--payment DATE:AMT` self-assessment payments after 31 March (234B runs on the reducing balance). - `--income-event DATE:TAX` tax on income that arose on that date (the 234C proviso relief; the script prints a VERIFY line reminding you of its condition). - `--rate` and `--threshold` are defaults — pass the verified values. The script rounds the base down to the nearest ₹100 and counts a part month as a full month; confirm both conventions for the year. Read its output as it is. Show 234C instalment by instalment, never as one figure — a single number cannot be checked by the CA. If tax is still unpaid, state the rupees per month it grows. ## Step 5 — prepare the challan for the CA to pay The CA logs in to incometax.gov.in -> e-File -> e-Pay Tax -> New Payment. Fill with your browser tool (Claude in Chrome, a Playwright/browser MCP, or the Codex browser), or give the CA these values: | Field | Value | |---|---| | PAN and name | From the PAN card; check how it renders on the confirm screen | | Assessment Year | The AY, not the FY | | Type of payment (minor head) | Advance Tax (100) during the year, Self-Assessment Tax (300) after it, Tax on Regular Assessment (400) against a demand — confirm the label on screen before selecting | | Tax, then surcharge, cess, interest, penalty, fee | Each in its own box, split exactly as in the working | Never lump interest into the tax box; a challan split wrongly reconciles badly for years. Then stop at the gateway — bank sign-in, OTP and the Pay click are the CA's. State the exact total, the minor head and the AY, and ask for the challan details (BSR code, challan serial / CIN, date) back for the working and the return (Schedule IT). ## Output and handover In `//ITR/`, dated, with PAN and AY in the name: the estimate with its assumptions block, the instalment table, the 26AS challan tie-out, the interest workings section by section (script output attached), and a one-page payment instruction with the exact amount and heads — never a payment. Hand over the amount, the minor head, the AY, the date by which paying stops further interest, and what is estimated versus actual, said plainly. - **Check before paying**: the AY on the challan is the AY of the working; the minor head matches the purpose; the tax / interest split matches the working; the TDS assumed is what 26AS supports; every gain date used for 234C relief comes from a broker statement in the folder. - A **Rules used** block for every date, percentage, rate, threshold and tolerance, with source URL and date checked, or marked "confirm on the portal / notification" with the section it comes from.