This guide covers India’s Goods and Services Tax (GST) process. It explains how to prepare and file GSTR-1, verify sales against tax invoices and e-invoice data, and reconcile GSTR-2B with your purchase register before deciding input tax credit (ITC). GST rules, return tables, portal screens and due dates can change, so confirm the current instructions for your registration and tax period on the GST Portal. This is general information, not individualized tax advice.
What you are filing and reconciling
GSTR-1 is the statement of outward supplies for a GST-registered business in India. Depending on the transaction, it contains invoice-level details for registered customers, specified interstate B2C transactions, exports, credit and debit notes, amendments, and HSN/SAC summaries. A nil GSTR-1 is still required when a normal or casual registered taxpayer has no business activity for the period.
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Sales reconciliation compares your accounting records and source invoices with the figures that will be reported in GSTR-1. Purchase reconciliation is a separate control: you compare your purchase register and supplier invoices with the data in GSTR-2B before determining ITC. GSTR-2B is an input to that review, not a replacement for checking statutory ITC conditions.
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1. Confirm your filing profile and tax period
Start with the registration details that control which return and frequency appear in your account. Record the following before importing any data:
- GSTIN and legal name for each registration, including separate registrations in different states.
- Whether the registration is normal, casual or another category with special filing rules.
- Financial year, return period and whether the account is set for monthly or quarterly GSTR-1 filing.
- Whether the business has opted for a quarterly scheme and remains eligible for it.
- Any cancellation, suspension, registration amendment or effective-date issue affecting the period.
The Portal FAQ describes standard due-date patterns as the 11th day of the succeeding month for monthly GSTR-1 filers and the 13th day after the quarter for quarterly filers, subject to government extensions. Treat those as descriptions of the standard schedule, not a substitute for checking the notification and return dashboard for the period you are filing.
2. Close the sales records before opening GSTR-1
Freeze the period in your accounting system first. A return prepared from an open sales register is difficult to audit because invoices, returns and adjustments can change while data is being uploaded.
Assemble the source documents
- Sales register and tax invoices, including invoices issued to registered and unregistered customers.
- Credit notes, debit notes and any amendments to earlier documents.
- Export invoices, shipping or export evidence and deemed-export documents where applicable.
- Advance receipts and later adjustments against those advances.
- Exempt, nil-rated and non-GST supplies.
- E-commerce supplies and related records when the transaction type requires separate reporting.
- Electronic invoice records and the invoice reference details returned by the Invoice Registration Portal.
Mark each transaction by GSTIN, customer type, state and transaction category before uploading. GSTR-1 tables depend on the nature of the supply; one undifferentiated sales total cannot reliably populate all required sections.
Build a period-control sheet
Create one control sheet for the period with totals from the ledger and totals that will appear in GSTR-1. Include taxable value, IGST, CGST, SGST or UTGST, cess where applicable, and the count of documents. Add separate lines for advances, notes, exports, exempt or nil-rated supplies, and amendments. This sheet lets you investigate a difference instead of discovering it after filing.
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3. Validate every invoice identity and classification
For each document that can affect the return, compare the accounting record with the source invoice. The following checks form a practical reconciliation checklist; not every field is required in every GSTR-1 table.
- Document identity: invoice, credit-note or debit-note number, document type and document date.
- Parties: supplier or recipient GSTIN where relevant, legal name and state.
- Amounts: taxable value, tax rate, tax amount and total value.
- Place of supply: state code and the resulting IGST or CGST/SGST treatment.
- Supply category: B2B, applicable B2C, export, deemed export, exempt, nil-rated, non-GST or e-commerce category.
- Amendment link: the original period and document reference when correcting a previously reported record.
Validate the recipient GSTIN status on the invoice date, not only its current status. An incorrect GSTIN or a wrong place-of-supply treatment can cause portal validation errors, customer credit mismatch or an incorrect tax liability.
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4. Use e-invoice data, then check it against your books
The National Informatics Centre states that invoice information is transferred from the Invoice Registration Portal to the GST Portal and the e-way bill portal in real time. The GST Portal uses that information to populate specified GSTR-1 tables, and the GSTR-1 manual says e-invoice details reach the return in a period of two days. These are portal process descriptions and can change.
Do not treat a populated table as proof that the sales register is complete. Download the available e-invoice details as Excel or use the relevant portal view, then perform three comparisons:
- Match the invoice number, date and supplier or customer GSTIN to the sales register.
- Compare taxable value, tax rate, tax amount and place-of-supply treatment.
- Search for invoices present in the books but absent from the feed, and for duplicates or invoices cancelled in the source system.
Investigate timing differences separately. An invoice issued near the period end may not yet appear in the return view, while an amendment or cancellation may require a different table. Keep a documented exception list and clear it before generating the final summary.
5. Choose a practical way to prepare GSTR-1
The GST Portal supports online entry, the GST Returns Offline Tool and third-party applications connected through GST Suvidha Providers (GSPs). Select the method based on transaction volume and the controls you need.
The Tool Desk
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|---|---|---|---|
| Portal entry | Low transaction volume or occasional corrections | Uses the current return-period screens and immediate portal validation | Manual keying can create omissions, duplicate documents and slower review |
| GST Returns Offline Tool | Businesses preparing larger batches in spreadsheets or JSON | Bulk preparation, local review and import/export before submission | Use the current utility version; retain the source file, error reports and final upload file |
| ASP application through a GSP | Recurring, high-volume or multi-registration filing | May support imports, validation rules, user roles and an audit trail | Confirm access controls, retention, amendment history, export capability, support and fees |
| GSTN Matching Offline Tool for GSTR-2B | Matching purchase registers to GSTR-2B | Downloads GSTR-2B JSON and displays supplier and document details for matching | Review match logic, exceptions and the final ITC decision manually |
Regardless of the method, retain an export of the data submitted and the exception report used to approve it. A tool that imports quickly but hides duplicate or mismatched invoices is not a complete control.
6. Enter, review and file GSTR-1
Portal labels change, so follow the current period’s dashboard rather than an old screenshot. The general sequence is:
- Open the return: Sign in to the GST Portal, select the relevant GSTIN, choose Returns, open the return dashboard, and select the financial year and tax period.
- Open GSTR-1: Choose the GSTR-1 tile and confirm the filing frequency and period displayed by the portal.
- Add or import records: Enter or upload B2B, applicable B2C, export, note, amendment, advance and other transaction data in the tables that apply to your supplies.
- Resolve validation errors: Correct invalid GSTINs, document numbers, dates, tax rates, place-of-supply codes and duplicate records in the source file or portal screen, then upload again if necessary.
- Complete the HSN/SAC summary: From May 2025 return periods, the manual states that the HSN summary is divided into B2B and B2C tabs. Use the layout displayed for your selected period.
- Generate the summary: Select the option to generate or preview the summary after all applicable tables are complete. Allow processing time if the portal shows a pending status.
- Compare totals: Reconcile taxable value, tax by type, document counts, notes, exports and exempt or nil-rated supplies to your period-control sheet.
- Proceed to filing summary: Open the filing summary, inspect every value and review any warning or liability message before confirming.
- File the return: Use the authentication method offered for the registration, such as the authorized signatory’s verification. Save the acknowledgement and filing reference immediately.
The filing manual cautions that values cannot be edited or deleted through the same pre-filing process once the statement is filed. Resolve errors before confirmation and preserve the underlying invoice, upload and approval records for any later amendment process permitted by law.
7. Reconcile purchases and GSTR-2B before claiming ITC
GSTR-2B is generated from supplier-reported data. Your purchase register remains the starting point for determining what the business bought, while the tax law and supporting documents determine whether credit is allowable.
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Prepare the two populations
- Export the purchase register for the same period, including invoices, debit notes, credit notes and reverse-charge transactions.
- Download GSTR-2B in the format offered for the period. GSTN’s Matching Offline Tool uses the GSTR-2B JSON and lets you view supplier and document details while matching them to the purchase register.
- Normalize invoice numbers, dates, GSTINs and tax amounts so formatting differences do not create false exceptions.
Match on decision-useful fields
Match at least supplier GSTIN, document number, document date, taxable value and tax amount. Classify each line as matched, partially matched, missing in GSTR-2B, missing in the purchase register, duplicate, or mismatched. A tolerance used for rounding should be documented and approved; it should not conceal a material tax difference.
Resolve exceptions
- Invoice in books but absent from GSTR-2B: Confirm the supplier filed the invoice in the relevant return, check the reporting period and request correction or reporting where appropriate.
- Different invoice number, date or value: Compare the original invoice and ask the supplier to amend its return if the supplier’s data is wrong.
- Duplicate: Check whether one record is an amended document, credit note or duplicate import. Do not claim the same credit twice.
- Credit note or reversal: Link it to the original invoice and account for the reduction required by law.
- Reverse charge: Identify the tax that the recipient must pay and the conditions for any related credit; do not assume that a GSTR-2B line settles the reverse-charge obligation.
The GST Portal advises reconciling GSTR-2B with the books, avoiding double claims, making reversals required by law and paying reverse-charge tax. A matched line can still fail other ITC conditions, such as business-use, possession of a valid document or statutory time limits. Have the responsible tax reviewer approve the final eligible amount.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.8. File the related return and retain evidence
After sales and purchase reconciliations are approved, open the current return dashboard for the registration’s filing frequency and complete the related return, including GSTR-3B where applicable. Quarterly taxpayers who are eligible and have opted for the scheme file both GSTR-1 and GSTR-3B quarterly, according to the Portal FAQ description. Confirm the current rule and any monthly payment or reporting requirement that applies to your scheme before filing.
Retain a period file containing:
- Sales and purchase registers used for the reconciliation.
- Tax invoices, credit and debit notes, export evidence and advance records.
- E-invoice downloads, upload files, validation errors and corrected versions.
- GSTR-1 and GSTR-2B downloads, match results and exception approvals.
- Working papers for reversals, reverse charge, amendments and ITC decisions.
- Filed return acknowledgements and payment or liability records.
Use consistent file names that include GSTIN, financial year, period and version. Restrict editing rights after approval and preserve a read-only copy of the final submission.
Common failure points and fixes
The portal rejects a GSTIN
Check the GSTIN against the invoice date, remove spaces or punctuation, and confirm that the customer belongs in the selected table. If the registration status changed, document the status used and obtain tax advice on the correct treatment.
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The e-invoice is missing from GSTR-1
Check whether the invoice has passed the portal’s stated transfer window, whether it was cancelled, and whether the period or table is correct. Compare the e-invoice download with the sales register and follow the portal’s current correction process rather than creating a duplicate manually.
Summary totals do not match the ledger
Reconcile by table and tax type, then isolate advances, notes, amendments, exports and exempt supplies. A single net total can hide a wrong classification that must be corrected at document level.
GSTR-2B does not match the purchase register
Normalize document-number formats, check supplier GSTIN and period, separate credit notes and reverse-charge entries, and send a supplier-wise exception list for correction. Keep unmatched items out of the eligible ITC calculation until the reviewer resolves their status under the applicable rules.
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The portal manual warns that the filed statement cannot be edited or deleted through the pre-filing screen. Record the error, identify the legally available amendment or adjustment route for the relevant period, and preserve the original filing acknowledgement and correction approval.
Period-end checklist
- Confirm GSTIN, registration type, frequency, financial year and tax period.
- Freeze the sales register and collect all invoices, notes, advances, exports and special-category supplies.
- Validate GSTIN status, document identity, amounts, tax rates and place of supply.
- Download and review e-invoice data; investigate omissions and duplicates.
- Prepare all applicable GSTR-1 tables and HSN/SAC summaries.
- Generate the current-period summary and compare it with the control sheet.
- Reconcile GSTR-2B to the purchase register and document every exception.
- Exclude duplicate or ineligible ITC, record reversals and address reverse charge.
- Review the filing summary with an authorized person before authentication.
- Save acknowledgements, source data and reconciliation evidence in the period file.
When to obtain professional help
Use a qualified GST professional when you have multiple state registrations, exports, e-commerce supplies, frequent amendments, substantial reverse-charge transactions, disputed ITC, a registration change, or a material mismatch that cannot be resolved with the supplier. The portal provides the mechanics; it does not decide every question of taxability, eligibility or accounting treatment.
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