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Mid-market and enterprise finance teams cannot manually clear 800-plus inward invoices through the IMS accept/reject/pending workflow within the six-day window between GSTR-2B generation on the 14th and GSTR-3B filing on the 20th. Manual processing risks ITC mismatches, Rule 36(4) compliance gaps, and DRC-01C notices.
An automated workflow pulls IMS data daily, joins it to the purchase register on supplier GSTIN plus invoice number plus tax period, recommends Accept for matched lines, Reject for orphans or amount mismatches, and Pending for review-needed exceptions. The exception queue routes to GSTIN owners with vendor follow-up tasks. Post-decision GSTR-2B is re-pulled and reconciled against accepted-set ITC for GSTR-3B preparation.
Daily IMS pull schedule, purchase-register-to-IMS field mapping, decision-recommendation thresholds (amount tolerance, date tolerance), vendor-follow-up SLA per Pending bucket, multi-GSTIN consolidation rules, and Rule 36(4) audit-trail capture per Accept timestamp.
Daily IMS decision queue with auto-recommended actions, exception report per GSTIN, GSTR-3B-ready ITC value reconciled against post-decision GSTR-2B, vendor follow-up workbook for Pending items, and Rule 36(4)-compliant audit pack for the period.
The GST Invoice Management System changed the operating shape of monthly ITC reconciliation. Before October 2024, GSTR-2B was a passive feed and reconciliation was a two-source compare between the purchase register and the portal-generated GSTR-2B. After IMS, every inward invoice requires an explicit Accept, Reject, or Pending decision before it flows into GSTR-2B. For an enterprise running 800 or more inward invoices a month, manual decision-making in the six-day window between the 14th and the 20th is operationally infeasible. This playbook describes the end-to-end automation workflow that mid-market and enterprise finance teams are adopting for FY 2026-27.
The IMS Workflow in One Diagram
The reconciliation pipeline now has six stages:
- Supplier files GSTR-1 (rolling, throughout the month).
- Invoice appears in buyer’s IMS dashboard on the GST portal.
- Buyer reviews and posts Accept, Reject, or Pending decision.
- GSTR-2B generated on the 14th, reflecting all IMS decisions to that point.
- Post-14th IMS actions update GSTR-2B until the 20th deadline.
- GSTR-3B filed by the 20th, with ITC claims drawn from the accepted-set in GSTR-2B.
The five-day buffer between stages 4 and 6 is the entire window for last-minute decisions. Volume forces automation.
Daily IMS Pull Cadence
Suppliers file GSTR-1 across the month, not in a single bulk on the 11th deadline. An invoice can appear in IMS as early as the 2nd or as late as the 13th. A daily pull schedule from the GST portal flattens the decision load across 20 working days rather than concentrating it into the post-14th window.
For an 800-invoice month, daily pulls deliver an average of 40 new invoices per working day. Most resolve automatically against the purchase register. The unmatched residue — typically 5 to 12 percent — is the human review queue.
A daily cadence also surfaces supplier-side errors early: an invoice filed under the wrong buyer GSTIN, a wrong invoice number, or a wrong tax period. Catching these on the 3rd of the month leaves time for the supplier to file a GSTR-1 amendment before the cycle closes, instead of forcing a Reject and a one-month ITC deferment.
Automatic Accept/Reject Decision Engine
The decision engine compares each IMS line against the purchase register on three keys: supplier GSTIN, invoice number, and tax period. Match outcomes drive recommended actions:
| Match Outcome | Recommended Action | Notes |
|---|---|---|
| Exact match on all three keys plus amount within tolerance | Accept | Auto-post |
| Exact match on keys, amount mismatch above tolerance | Pending | Route to vendor follow-up |
| IMS line with no purchase-register match | Reject | Likely supplier error or invoice not received |
| Purchase-register line with no IMS match | Pending external | Supplier has not filed; track for next month |
| IMS line matches a credit note in purchase register | Accept with reversal flag | Section 34 of the CGST Act treatment |
Amount tolerance is typically ₹1 or 0.1 percent — narrow enough to catch real differences, wide enough to ignore rounding. Date tolerance is rarely needed since tax period is monthly.
The engine produces a decision recommendation per line. Finance teams review and override exceptions; everything else flows through.
Pending-Bucket Review Queue with Vendor Follow-Up
Pending is the operational risk zone. An invoice left in Pending past 30 days is treated as Accepted by default under the IMS rules — the buyer loses the chance to Reject after that point. A disciplined Pending queue has three sub-buckets:
- Vendor follow-up required: Amount or detail mismatch needing supplier confirmation. SLA: vendor response within 7 working days.
- Internal verification needed: Invoice not yet logged in purchase register but supplier has filed. SLA: AP team confirmation within 5 working days.
- Hold for documentation: Invoice received but goods-receipt note not yet generated. SLA: warehouse confirmation within 10 working days.
Each sub-bucket has an owner, an SLA, and an escalation path. Pending items at day 25 trigger a final-review alert before the 30-day deemed-accept threshold.
GSTR-3B Preparation from the Accepted Set
GSTR-3B Table 4 ITC values must equal the ITC in the post-decision GSTR-2B, adjusted for Section 17(5) blocked credits and Rule 37 reversals for unpaid invoices past 180 days.
The accepted set from the IMS pipeline is the upstream input. Once IMS decisions are posted and GSTR-2B re-pulled, three reconciliations run before GSTR-3B is prepared:
- Accepted IMS lines = GSTR-2B lines (sanity check).
- GSTR-2B ITC minus Section 17(5) blocked = eligible ITC.
- Eligible ITC minus Rule 37 reversals = GSTR-3B Table 4 ITC.
The audit trail captures all three reconciliations so a future GST audit can trace every rupee of ITC from supplier invoice to ledger entry.
What is your ITC leakage actually costing?
The ITC Leakage Calculator quantifies the annual rupee cost of ITC blocked by supplier non-filing under the IMS regime. Five inputs return permanent leakage, working-capital lock, and analyst hours.
Run the ITC Leakage Calculator →Rule 36(4) Audit Trail Signature
Rule 36(4) of the CGST Rules requires that ITC be claimed only against invoices appearing in GSTR-2B. The IMS layer adds an explicit Accept decision as the new evidentiary step. Audit packs must now include:
- Purchase register entry with date and amount.
- IMS Accept timestamp captured from the GST portal.
- Corresponding GSTR-2B line with summary totals.
- GSTR-3B Table 4 figure tying back to the accepted set.
- Proof of supplier payment within 180 days (Rule 37).
The IMS Accept timestamp is the new artefact. Spreadsheet-based reconciliation rarely captures it; an automated workflow does so by default when posting decisions to the portal.
Multi-GSTIN Consolidation
For groups with 3 to 15+ GSTINs, the consolidated workflow runs the same decision logic across all GSTIN dashboards. A shared purchase master with state-to-GSTIN mapping ensures each invoice is evaluated against the correct entity. Inter-state stock transfers within the group surface as paired IMS entries — one IMS Accept on the receiving GSTIN matched to a GSTR-1 filed by the dispatching GSTIN.
Centralised review and decentralised override is the common pattern: a shared service centre runs the automated decisions; state finance owners override exceptions on their GSTIN.
Monthly Cadence vs Daily Processing: Impact on Close Cycle
Teams that adopt daily IMS processing typically compress their monthly close by 2 to 3 days. The 14th-to-20th window stops being a bottleneck because most decisions are already posted by the 14th. GSTR-3B preparation becomes a one-day activity instead of a three-day scramble.
Tools like a GST reconciliation software built for the IMS regime expose the daily-pull, decision-engine, and audit-trail capture as a single workflow. For multi-process reconciliation contexts where GST sits alongside TDS, bank, and payment-gateway flows, an integrated reconciliation software India approach reduces duplicate data movement.
Worked Example: 800 Invoices, Mid-Market Manufacturer
A mid-market manufacturer with 800 monthly inward invoices and a single GSTIN runs the daily IMS pull. Distribution across a representative month:
- 642 invoices auto-Accepted (exact match, amount within tolerance) — 80 percent.
- 96 invoices auto-Rejected (no purchase-register match — supplier errors, mostly other-GSTIN filings) — 12 percent.
- 48 invoices Pending vendor follow-up (amount mismatch) — 6 percent.
- 14 invoices Pending internal verification (purchase not yet logged) — 2 percent.
Daily handling: 40 invoices per working day, of which 32 auto-Accept, 5 auto-Reject, and 3 land in Pending. The finance team reviews 3 to 5 exceptions per day — a 30-minute activity.
By the 14th, 760 of the 800 invoices have decisions. The post-14th window handles the residual 40 Pending items, of which 35 resolve through vendor follow-up and 5 carry forward to next month’s IMS cycle. GSTR-3B is prepared on the 16th and filed on the 18th — a two-day buffer before the deadline.
This is the operating shape of IMS reconciliation when automation is in place. For a comparison of the underlying decision framework, see IMS vs GSTR-2B reconciliation, the related GSTR-2B reconciliation guide, and the GSTR-1 vs GSTR-3B reconciliation cross-check that closes the loop on outward supplies.
For the canonical IMS reference and dashboard access, the GST portal hosts the live system under the GSTR-2B services menu.