IDS refund under Rule 89(5) from 1 Nov 2026: new formula calculator & ledger
Upload your purchase register (CSV or Excel, e.g. a Zoho Books bills export), tag each line as input, input service or capital good, and get Net ITC and the Maximum Refund Amount for inverted duty structure — step by step, with the 1 Nov 2026 availment split done for you.
- Runs 100% in your browser — files are never uploaded
- No login, no GST portal access
- Free calculation · paid export
Not tax advice. Does not file RFD-01. Independent of GSTN and the GST portal.
Calculator
1 Purchase register (bills / ITC)
Match each field to a column in your file. Every mapping is editable. Unmapped amount columns count as 0.
2 Classify lines
Categories: input · input_service · capital_good · ineligible. HSN/SAC rule: SAC starting with 99 → input_service. Eligibility is set automatically from the ITC availed date.
| # | Invoice | Inv. date | ITC availed | Supplier GSTIN | HSN/SAC | Description | ITC | Category | Eligible | Counted | Reason |
|---|
3 Relevant period & turnover
Sales CSV columns: period,turnover_inverted,adjusted_total_turnover,tax_payable_inverted (rows are summed; period YYYY-MM sets the months).
4 Result free preview
Load a purchase register and enter the turnover figures to see the result.
5 Export
Full downloads (line-by-line ledger CSV/XLSX, summary PDF, Annexure B draft CSV) need an unlock code.
The code is checked inside your browser against a list of code fingerprints. Nothing is sent anywhere.
Annexure B export is a draft listing of the invoices counted in Net ITC. It has not been checked against the official GST offline utility format — do not upload it as-is.
What changed in Rule 89(5) on 1 November 2026
Notification 05/2026–Central Tax (26 Oct 2026) substituted sub-rule (5) of Rule 89 of the CGST Rules with effect from 1 November 2026. The refund of unutilised ITC on account of an inverted duty structure is now:
Maximum Refund Amount = (Turnover of inverted rated supply × Net ITC ÷ Adjusted Total Turnover) − tax payable on such inverted rated supply
- Net ITC = ITC availed on inputs + ITC on eligible input services during the relevant period + ITC on capital goods attributable to the relevant period.
- Eligible input services = input services on which ITC was availed on or after 1 Nov 2026. Earlier availments do not count, so periods around the change need a line-by-line split by availment date.
- Capital goods count only where ITC is availed on or after 1 Apr 2027: 1/60 of the ITC for each month of the relevant period inside the 60-month window, minus reversals.
- The old reduction factor on the tax-payable term (× Net ITC ÷ ITC on inputs and input services) no longer applies.
- An inverted structure still means the rate on inputs is higher than on the output supply. A higher rate on input services alone does not create one.
The old formula for periods before 1 Nov 2026 was: (Turnover of inverted rated supply × Net ITC ÷ ATT) − tax payable × (Net ITC ÷ ITC on inputs and input services), with Net ITC from inputs only. The calculator offers it for those periods. For periods that straddle 1 Nov 2026 the transition treatment is not settled here, so we recommend filing periods that start on or after November 2026.
Worked example (synthetic data)
| Bill | Type | ITC availed | ITC (₹) | In Net ITC? |
|---|---|---|---|---|
| B-001 steel coil | input | 10 Nov 2026 | 18,000 | Yes |
| B-002 IT consulting | input service | 10 Nov 2026 | 3,600 | Yes (availed ≥ 1 Nov 2026) |
| B-003 audit fee | input service | 25 Oct 2026 | 1,800 | No (availed before 1 Nov 2026) |
| B-004 laptop | capital good | 12 Nov 2026 | 10,800 | No (only from 1 Apr 2027) |
Net ITC = 18,000 + 3,600 = 21,600. With turnover of inverted rated supply ₹5,00,000 and Adjusted Total Turnover ₹5,00,000:
- Tax payable on inverted supply ₹25,000 → 21,600 − 25,000 = −3,400 → Maximum Refund ₹0.
- Tax payable on inverted supply ₹6,000 → 21,600 − 6,000 = Maximum Refund ₹15,600.
FAQ
Is my data uploaded anywhere?
No. Files are read and processed by JavaScript in your browser tab. There is no server, no account and nothing is stored. Closing the tab clears everything.
Does it work with a Zoho Books export?
Yes, through column mapping. The "Zoho Books Bills export" preset holds best-guess column names that we have not yet checked against a live export. Check the mapping, fix any column, then apply. Generic CSV/XLSX registers work the same way.
What if my file has no ITC availed date?
The invoice date is used instead, with a warning. For input services near 1 Nov 2026 the availment date decides eligibility, so add the real date where you can.
Why are my capital goods showing 0?
Under the substituted rule, capital goods enter Net ITC only where ITC is availed on or after 1 April 2027, spread at 1/60 per month. Until then their contribution is zero.
Can it compute periods before November 2026?
Yes. For periods ending before 1 Nov 2026 you can switch to the old formula (Net ITC from inputs only). Periods that straddle 1 Nov 2026 show a warning, because the transition treatment is not settled here.
Is the Annexure B export ready to upload?
No. It is a draft listing of the invoices counted in Net ITC, to help you prepare the statement. It has not been checked against the official offline utility format.
What does the unlock code cover?
One code unlocks the downloads (ledger CSV/XLSX, summary PDF, Annexure B draft) in your browser for one GSTIN and one period. The calculation and totals are free to view.
Does this file my refund or talk to the GST portal?
No. It does not submit RFD-01, does not log in to the GST portal and is not affiliated with GSTN or CBIC.
Disclaimer
IDS Ledger is a calculation aid, not tax, legal or accounting advice. It does not submit Form GST RFD-01 or any return, and it is independent of GSTN, CBIC and the GST portal. Results depend entirely on the data and classifications you enter. Verify every figure against Notification 05/2026–Central Tax, the CGST Rules and your own records, or with a qualified professional, before you file anything.