GST ITC Reconciliation, IMS, E-Invoicing, HSN Codes and Registration Amendment — Rules, Limits and Monthly Routine
Quick answer: Input tax credit is now controlled by what the supplier reports and what the recipient does with it: GSTR-2B is a static statement generated on the 14th of the month, the Invoice Management System (IMS, live from October 2024) lets the recipient accept, reject or keep pending each supplier record, and records with no action are treated as accepted when GSTR-2B is generated. E-invoicing is mandatory once aggregate turnover has exceeded ₹5 crore in any year since 2017-18, and from 1 April 2025 taxpayers with turnover of ₹10 crore or more cannot report an invoice to the IRP after 30 days. HSN codes need four digits up to ₹5 crore and six digits above it, and a change in registration particulars is filed in Form GST REG-14 within 15 days. Credit that is not in GSTR-2B, or is claimed after the Section 16(4) deadline, is the usual source of notices.
Last verified 5 October 2026 — rules on this page checked against the current notifications. We update it the day a rule changes.
The monthly ITC routine
| Step | What to do | Why |
|---|---|---|
| 1. Draft GSTR-2B (14th) | Open the draft built from suppliers' GSTR-1/1A/IFF and your IMS actions | GSTR-2B is the statement ITC is claimed against; GSTR-2A is a dynamic view that keeps changing |
| 2. Reconcile to books | Match supplier-wise invoices, credit notes and amendments with the purchase register; list missing, extra and value-mismatch items | Differences are what ASMT-10 notices later ask about |
| 3. IMS actions | Accept valid records, reject wrong ones, keep pending those you cannot yet verify | No action means deemed accepted |
| 4. Recompute and claim | Recompute GSTR-2B after IMS changes, then file GSTR-3B with ITC no higher than GSTR-2B shows | The portal auto-populates GSTR-3B and warns on upward edits under Rule 36(4) |
| 5. Chase and reverse | Follow up suppliers on missing records; reverse credit where the supplier is unpaid beyond 180 days or the item is blocked | Section 16(4) deadline, Rule 37 reversal and Section 17(5) blocks |
Invoice Management System (IMS)
- Facility on the GST portal since October 2024 where records saved or filed by suppliers in GSTR-1, GSTR-1A and the IFF reach the recipient to accept, reject or keep pending
- Accepted records enter the ITC Available section of GSTR-2B and auto-populate GSTR-3B; rejected records go to ITC Rejected; pending records stay in IMS and are in neither GSTR-2B nor GSTR-3B; no action is deemed acceptance when GSTR-2B is generated
- Pending is not available for some record types, and reverse-charge documents are not part of IMS; a rejected or pending record can be changed and GSTR-2B recomputed before filing GSTR-3B
E-invoicing — who, when, by when
| Point | Rule |
|---|---|
| Applicability | Aggregate annual turnover above ₹5 crore in any financial year from 2017-18 onwards (Notification 10/2023-Central Tax, effective 1 August 2023), checked at PAN level, subject to notified exclusions |
| What it means | Invoices, credit and debit notes are reported to the Invoice Registration Portal to get an IRN and QR code; an invoice without one is not a valid tax invoice for the buyer's credit |
| 30-day reporting | From 1 April 2025, taxpayers with turnover of ₹10 crore or more cannot report an invoice, credit note or debit note after 30 days from its date — the portal rejects it |
| Below ₹5 crore | Not mandatory; B2B invoices still carry the correct HSN and details for the buyer's GSTR-2B |
HSN / SAC, rate classification and registration changes
- HSN digits: up to ₹5 crore turnover — 4 digits on B2B invoices (optional for B2C); above ₹5 crore — 6 digits; services use SAC codes. Wrong digits cause GSTR-1 rejection and mismatches at the buyer
- Rate advisory: rates are fixed item by item by notification and the structure was reset in 2025, so we confirm the rate, exemption and condition on the date of supply and keep a classification note for audits — see GST audit and health check
- GST amendment (REG-14): a change in business name, place of business, partners or directors, or contact details is filed within 15 days of the change; changes to core fields need the officer's approval, others take effect on filing; update e-way bill and e-invoice master data afterwards — see registration
What we do
- Monthly 2B-to-books reconciliation with an exceptions list, IMS action and supplier follow-up; ITC reversal workings
- E-invoicing set-up and the 30-day monitor, HSN master clean-up, REG-14 amendments, classification notes
- Pairs with GST return filing, ASMT-10 replies and e-way bill compliance
Dates, forms and thresholds are quoted from the governing Act, rules and official portals; where a figure changes by notification or year, the page says so and we confirm it at filing rather than estimate.
Talk to us before you file anything
Frequently asked questions
What is the Invoice Management System in GST?
A portal facility since October 2024 that lets a recipient accept, reject or keep pending each invoice or credit note reported by suppliers in GSTR-1, GSTR-1A or the IFF, which then drives GSTR-2B.
What happens if I take no action in IMS?
The record is treated as deemed accepted when GSTR-2B is generated on the 14th, and it appears in ITC Available.
What is the difference between GSTR-2A and GSTR-2B?
GSTR-2A is a dynamic view that changes as suppliers file; GSTR-2B is a static statement generated for each month on the 14th and is the basis for claiming ITC.
What is the e-invoicing limit?
Mandatory where aggregate annual turnover has exceeded ₹5 crore in any financial year since 2017-18, effective 1 August 2023 under Notification 10/2023-Central Tax.
What is the 30-day e-invoice reporting rule?
From 1 April 2025, taxpayers with turnover of ₹10 crore or more cannot report invoices, credit notes or debit notes to the IRP more than 30 days after their date.
How many HSN digits are required?
Four digits on B2B invoices up to ₹5 crore turnover and six digits above ₹5 crore.
What is the time limit to amend GST registration details?
Within 15 days of the change, in Form GST REG-14; core-field changes need the officer's approval.
Can I claim ITC that is not in GSTR-2B?
The portal limits GSTR-3B credit to what GSTR-2B shows, so the supplier must report the invoice or the recipient must wait; claims after the Section 16(4) deadline are lost.