Drafting GSTR-1 and GSTR-3B with AI: A Table-by-Table Guide

AI helps most with GST return preparation once reconciliation is already done — turning a reconciled purchase and sales position into draft GSTR-1 and GSTR-3B tables you review rather than build from scratch. The value is concentrated in specific tables, not the return as a whole, and some tables need more of the CA's attention than others regardless of how automated the drafting is. This piece goes table by table through GSTR-1 and GSTR-3B, covers the QRMP/IFF wrinkle, and sets out the cross-return checks that matter before you authorise a filing. For the wider landscape of AI across the GST compliance calendar — IMS, notices, the deadlines themselves — see How AI Is Changing GST Compliance for Indian CAs; this piece drills into return preparation specifically.

GSTR-1: drafting outward-supply tables from the sales register

GSTR-1 reports outward supplies in structured tables, and AI drafting tools generally handle each with different confidence:

• B2B invoices (Table 4) — drafted reliably from the sales register, provided GSTINs and invoice details are clean. This is largely a formatting and validation exercise once the underlying data is correct.
• B2C supplies (Table 7) — summarised by rate and, for larger B2C transactions, by place of supply. Errors here are usually a place-of-supply classification issue rather than a data problem, so this table deserves a second look even after AI drafting.
• HSN summary (Table 12) — drafted from the HSN codes already assigned to items in the accounting system. The AI step is aggregation; the classification itself should have been decided (and periodically reviewed) separately, since a wrong HSN code carried forward automatically just compounds the error at scale.
• Amendments (Table 9) — this is where AI drafting earns its keep, since amendments to prior-period invoices are easy to lose track of manually and easy for a tool to carry forward correctly once flagged.
• E-invoice reconciliation — for taxpayers under e-invoicing, GSTR-1 should tie to the Invoice Registration Portal data. A drafting tool that cross-checks the sales register against IRP-generated invoices before populating GSTR-1 catches a mismatch here before it becomes a filing-time scramble.

GSTR-3B: the table-by-table review

GSTR-3B is a summary return, and each table draws on a different underlying process:

• Table 3.1(a)–(c) — outward taxable supplies — drafted from the same sales data as GSTR-1, which is exactly why a 1-vs-3B consistency check (below) matters: both tables should tell the same story from different angles.
• Table 3.1(d) — inward supplies liable to reverse charge — the table most firms under-report without realising it, since RCM liability on import of services, GTA, legal fees from an advocate, and similar categories requires someone to actively flag the transaction rather than wait for a supplier invoice to trigger it. AI drafting only catches this reliably if the underlying transaction is tagged as RCM-liable in the books in the first place — confirm this tagging discipline exists before trusting the table.
• Table 4(A) — ITC available and Table 4(B) — ITC reversed — this is the direct output of your reconciliation, described in depth in How to Automate GST Reconciliation with AI. A tool that carries the reconciled figure across automatically removes the transcription step where a typo between the workpaper and the return most often creeps in.
• Table 5 — exempt, nil-rated, and non-GST supplies — drafted from the sales register's classification tags; worth a periodic audit of the tags themselves, since a supply wrongly marked exempt understates tax rather than just misclassifying a line.
• Table 6.1 — payment of tax — the final computation, drawing on the liability and credit tables above. This is arithmetic once the inputs are right, which is exactly where AI is strongest and human review is least necessary — provided the inputs were reviewed upstream.

The QRMP and IFF wrinkle

Taxpayers on the Quarterly Return Monthly Payment (QRMP) scheme (turnover up to ₹5 crore) file GSTR-1 quarterly but may push B2B invoices through the Invoice Furnishing Facility (IFF) in the first two months of the quarter, with the balance going into the quarterly GSTR-1. A return-prep tool needs to track which invoices already went through IFF so the quarterly return does not duplicate them — a narrower, more specific feature than basic monthly drafting, and one worth confirming explicitly with any vendor rather than assuming it is covered.

For GSTR-3B under QRMP, monthly tax payment (via a fixed-sum or self-assessment method) still needs tracking between the actual quarterly return filing dates, which shift to the 22nd or 24th depending on the state grouping. A drafting tool that ignores this and treats every client as a monthly filer will produce a table that is technically correct but filed against the wrong deadline logic.

Cross-return consistency checks before you file

The single most valuable automated check in return preparation is comparing GSTR-1 and GSTR-3B against each other before either is filed, because a gap between the two is one of the more common triggers for a scrutiny notice later:

• Outward turnover in GSTR-1 vs Table 3.1 of GSTR-3B for the same period — any material gap should be explained (a timing difference, an amendment) before filing, not discovered months later.
• ITC claimed in GSTR-3B vs what your reconciliation supports from GSTR-2B — the check covered in depth in the reconciliation-focused pieces linked above, but worth re-confirming at the point of drafting 3B specifically, since a late change to the purchase register after reconciliation can silently break this tie.
• RCM liability declared vs RCM ITC claimed — these should generally move together; a liability with no corresponding credit claim (or vice versa) is worth a second look before filing.

A tool that surfaces these three checks as a pre-filing gate, rather than leaving them to be discovered at GSTR-9 time, is doing meaningfully more than "drafting a return."

What still needs the CA's own review

• Blocked credits under Section 17(5) — motor vehicles, food and beverage, club memberships, and construction-related inputs need to be kept out of Table 4(A) regardless of what the reconciliation technically matched.
• RCM transaction tagging — the accuracy of Table 3.1(d) depends entirely on whether the books correctly flagged the transaction as RCM-liable in the first place; a drafting tool inherits this error if it exists upstream.
• Classification and place-of-supply calls — B2C table accuracy and IGST-vs-CGST/SGST splits depend on judgement the tool cannot make.
• Tie-out to the financials — the return should reconcile to the books at a level a partner can explain if questioned, not just internally foot within the return.

A practical drafting sequence

1. Reconcile the purchase register against GSTR-2B first, so Table 4(A)/4(B) draft from a verified number, not a provisional one.
2. Confirm RCM and exempt-supply tagging in the books before drafting, since Table 3.1(d) and Table 5 inherit whatever tagging discipline already exists.
3. Draft GSTR-1 and GSTR-3B together, running the 1-vs-3B consistency check before either is finalised, not after both are filed.
4. Review the exceptions the drafting tool flags, in the same disciplined way you would review a reconciliation exception list.
5. Authorise filing only after the tie-out to financials is confirmed, since that is the check no automation substitutes for.

Frequently asked questions

Which GSTR-3B tables does AI draft most reliably?

Table 3.1 (outward supplies) and Table 4(A)/4(B) (ITC availed and reversed) draft most reliably because they flow directly from data you have already reconciled — sales register and purchase-register-to-2B matching respectively. Table 3.1(d) reverse-charge liability and Table 6.1 (tax payment) need closer review because they depend on transactions that are easy to under-report, like import of services.

Can AI handle GSTR-1 for a client on the QRMP scheme with monthly IFF filings?

Yes, and this is one of the clearer automation wins — the tool tracks which invoices have already gone through the Invoice Furnishing Facility in months one and two of the quarter, so the quarterly GSTR-1 does not duplicate them. Confirm this specifically with any vendor, since QRMP/IFF handling is a narrower feature than basic monthly GSTR-1 drafting.

Does AI check that GSTR-1 and GSTR-3B are consistent with each other before filing?

A good return-prep tool runs this check automatically, since GSTR-1 and GSTR-3B report overlapping information (outward turnover) from different angles and a gap between them is one of the most common triggers for a scrutiny notice. Confirm the tool flags the gap before filing, not just at annual-return time.

What does the CA still need to check before authorising an AI-drafted return?

Blocked credits under Section 17(5), the correctness of reverse-charge entries, classification and place-of-supply judgement calls, and that the return ties to the underlying financials — none of which an AI draft can certify on its own. The AI prepares the numbers; the CA's review decides they are right.

The takeaway

AI-assisted return preparation is strongest exactly where the inputs are already clean and verified — outward supplies from the sales register, ITC from a completed reconciliation — and weakest where upstream tagging discipline (RCM, exemptions, HSN) is inconsistent, because a drafting tool inherits whatever error already exists in the books. Run the GSTR-1-to-3B consistency check before filing, not after, and keep blocked credits, classification, and the tie-out to financials as the CA's own review, regardless of how automated the drafting becomes. Tools such as SmartLedger AI, Vyapar TaxOne, and ClearTax build around this draft-and-review workflow — see the GST filing category to compare current options.

Primary sources

AI output on GST is only as good as the law it is checked against. Verify rates, due dates and procedure at source before advising a client:

• GST Portal — returns, due dates and taxpayer services
• CBIC-GST — the CGST Act, rules, notifications and circulars
• ICAI — professional guidance and announcements for members