GSTR-3B is the monthly summary return: you declare totals and pay tax, rather than listing documents. xMatix Compute uses a same-GSTIN, same-period GSTR-1, the latest matching GSTR-2B statement, and tax-ledger data. For GSTR-1 it prefers a Filed record, but if none exists it falls back to a Draft record; filing is therefore a review preference, not a hard Compute prerequisite.
What fills each box
| Box | What it is | Computed from |
|---|---|---|
| 3.1(a)–(c) | Taxable outward, zero-rated, nil/exempt supplies | The selected same-period GSTR-1: Filed first, otherwise Draft |
| 3.1(d) | Inward supplies under reverse charge | Your tax ledger's reverse-charge purchase lines |
| 3.1.1 | E-commerce section 9(5) supplies | Manual — never computed |
| 4A | ITC available (imports, ISD, reverse charge, regular B2B) | The latest same-period GSTR-2B; rows stored with IMS status R are excluded |
| 4B | ITC reversed | Your ledger's blocked credit, plus the Rule 37 tracker's 180-day reversals |
| 4D | Ineligible ITC (disclosure) | Rule 37 reclaims plus the statement's not-available rollup |
| 6.1 | Payment of tax | Compute creates or refreshes payable rows per tax head; you retain and complete the cash and credit-utilization evidence |
Two design points explain most questions about these boxes:
- Outward figures follow the selected GSTR-1. Compute orders a Filed record before a Draft record, then uses filing date and record identity to resolve a tie. It does not refuse a Draft source when no Filed record exists.
- Reversals and reverse charge come from your ledger, not the statement. The portal's statement cannot know which credits you blocked or your reverse-charge workings; those are read from your own tax lines.
Prerequisites
- The period's GSTR-1 processed. Filed is preferred, but the on-demand Compute action can use a Draft same-period return.
- The period's GSTR-2B statement in place, portal side included.
- Purchase bills posted, so the Rule 37 tracker can see payment status.
Procedure
- 1
Label should identify the GST registration and filing period for reviewers.
- 2
GSTIN determines the registration whose liabilities and credits are computed.
- 3
Return Period fixes the statutory month or quarter represented by this snapshot.
- 4
Is Nil Return is a statutory declaration, not a shortcut for an unprocessed period.
- 5
Processed Invoice Value is not currently assigned by Compute and may remain blank; it is not completion evidence.
The header's Processed Invoice Value is not assigned by the current GSTR-3B Compute service. It may legitimately remain blank after Status becomes Computed, so do not use that field as evidence that Compute succeeded. Verify the status, child tables and source totals instead.
Step 1 — Compute
Open the return and verify its label, GSTIN, return period and Draft status. Identify the GSTR-1 that source selection will use—Filed first, otherwise Draft—and the latest matching GSTR-2B, then run Compute and wait for Computed status. Reconcile the generated child rows to those exact sources. The same pass refreshes derived boxes and the Rule 37 tracker, creating each overdue reversal or later reclaim once even when Compute is repeated.
Step 2 — Review the boxes, complete the manual rows
Review every auto-filled row against its named source and drill material totals before entering manual values. The rows the platform cannot know are yours to enter and are never touched by a recompute:
- box 3.1.1 (e-commerce 9(5) supplies),
- import-of-services ITC in 4A,
- a Rule 42/43 proportional reversal you have worked out (see ITC management),
- non-GST outward supplies,
- and the cash-paid and credit-utilization amounts in the payment table.
Recompute after late postings, compare the change report with those postings, and confirm manual rows remain. A manual row survives; a direct edit to a derived row does not. Make any permitted derived adjustment only after the final compute and retain its approval.
Step 3 — Record the tax payment
Compute upserts the payable amount for IGST, CGST, SGST and Cess while retaining the payment fields on existing rows. Enter or verify cash paid and each credit-ledger utilization from the portal challan/electronic-ledger evidence. Verify utilization does not exceed available ledger balances and the tax-head total settles the declared liability. These rows feed annual-return Table 9, so reconcile them to the portal before filing.
Step 4 — File and record the filing
After an authorized reviewer signs off the boxes and payment reconciliation, file on the portal. Record the acknowledgment number and filing date on the xMatix return, then verify status becomes Filed and Compute is unavailable. Preserve the portal acknowledgment; a filed return is a statutory snapshot and later corrections follow the amendment process.
Expected result
The Computed return draws derived boxes from the selected same-period GSTR-1, latest GSTR-2B and tax ledger, preserves reviewed manual rows, and reconciles tax payment by head. Filing evidence is recorded once and freezes the return against recomputation.
Scheduled computation
The compute can run unattended (finance.gstr3b.process on a schedule). The scheduled job skips Filed GSTR-3B records and treats its source inputs as ready only when both the matching GSTR-1 and GSTR-2B have a non-null ProcessedInvoiceValue. It does not require GSTR-1 Status to be Filed. This readiness rule is separate from the on-demand Compute action, which can compute even though GSTR-3B's own Processed Invoice Value remains blank.
Common problems
Box 3.1 is zero. Verify which same-GSTIN, same-period GSTR-1 was selected. Compute prefers Filed but can use Draft; zero usually means the selected return has no supported outward rows, was not processed, or belongs to a different GSTIN or period. File status by itself is not the diagnostic.
A credit you expected is missing from 4A. Check whether the source GSTR-2B row carries imported IMS status R, whether the latest matching statement contains the expected portal line, and whether the credit is blocked in your ledger. xMatix does not currently expose a supported GSTR-2B Accept/Reject action; only a stored IMS value supplied through an authoritative import or integration affects this filter.
Processed Invoice Value is blank after Compute. That is current behavior: Compute sets status and child rows but does not populate this header field. Validate the generated tables instead.
A figure you typed into a derived row vanished. A recompute replaced it — derived rows track their sources. Re-apply the adjustment after the final compute, or record it in the manual row it belongs to.