Online HSN Validator GST Portal: Rules & Digit Limits [2026]

The Harmonised System of Nomenclature (HSN) and Service Accounting Codes (SAC) are standardized classification systems that categorize goods and services to apply the correct GST rates. To prevent tax evasion and improve data consistency, the GSTN has implemented automatic HSN validation checks on the GST portal.

When uploading your monthly GSTR-1 sales returns, the portal automatically validates your HSN declarations in Table 12 against the CBIC master database. If you declare non-existent or deprecated HSN codes, the portal flags these entries, blocking the return upload or generating warning notices. This guide explains HSN validation rules, digit requirements, and how to verify code status.

1. Mandatory HSN Digit Requirements

Under Notification No. 78/2020-Central Tax, HSN digit requirements are determined by your Aggregate Annual Turnover (AATO):

2. How the Portal's Online HSN Validator Works

When you upload your GSTR-1 JSON payload or enter records manually, the portal runs an automated check on Table 12:

• Database Check: The validator matches each HSN code against the master registry. The registry contains approximately 20,000 valid 4-digit, 6-digit, and 8-digit codes.
• Turnover Level Check: If your AATO is above Rs 5 crore and you declare a 4-digit HSN code, the validator will flag it as an error, requiring a minimum of 6 digits to proceed.
• Unit Quantity Code (UQC) Check: The portal also verifies that the UQC declared (e.g. KGS, PCS, BOX, NOS) matches the standard measurement unit defined for that specific HSN code in the customs tariff directory.

3. Step-by-Step: Searching for HSN Codes on the GST Portal

Before configuring stock items in TallyPrime, use the portal's HSN search tool to confirm codes are valid:

1. Log into the GST portal and navigate to the home screen.
2. Go to Services > User Services > Search HSN/SAC.
3. Choose to search by HSN Code or Description.
4. Enter the search value. For example, search 6109 (T-shirts).
5. The portal displays the full 8-digit tariff code, the description of goods, the applicable GST rate, and the status (Active or Inactive).
6. If the status shows Inactive, do not use the code. You must use the updated replacement code issued by the CBIC.

4. Consequences of Entering Invalid HSN Codes

Failing to validate HSN codes before filing can lead to processing errors:

• GSTR-1 Upload Errors: The portal will display error messages like "HSN code not found in the master list" during JSON imports, requiring manual corrections inside Table 12 before you can file the return.
• E-Way Bill Generation Blocks: The e-way bill portal uses the same master database. If your invoice contains an invalid HSN, the system will block e-way bill generation, delaying your shipments.
• Audit Scrutiny: Declaring incorrect HSN codes to bypass validation checks can trigger audit scrutiny notices under Section 61, requiring you to explain rate discrepancies.

5. Resolving HSN Errors in TallyPrime

If TallyPrime flags HSN errors during your GSTR-1 return compilation:

1. Go to Gateway of Tally > Display More Reports > GST Reports > GSTR-1.
2. Navigate to the Uncertain Transactions section.
3. Look for the error category HSN/SAC details not provided or invalid.
4. TallyPrime lists all affected transactions. Select them, enter the corrected HSN code, and press Enter to update the vouchers.

6. HSN vs. SAC: Key Formatting Differences

While HSN codes classify physical goods, SAC codes classify service transactions. SAC codes are always 6 digits long and start with the number 99 (e.g. 9983 for Professional/Technical services). Ensure your accounts team groups service ledgers under the correct SAC code range, as the portal validator treats goods classifications and service classifications differently during return processing.

7. Keeping Tariff and Rate Tables Updated Natively

The CBIC occasionally updates the HSN tariff list, especially during Union Budgets or GST Council meetings where rates are modified. Ensure your TallyPrime database is regularly updated with the latest statutory files. With an active TSS subscription, TallyPrime updates these master tariff tables in the background automatically, helping you avoid compliance errors.

8. CBIC Notification Updates for E-way Bills

The e-way bill system requires matching HSN codes with GSTR-1 declarations. Exceeding turnover limits requires generating 6-digit codes for e-way bills to prevent transport vehicle blocks during transit checking.

9. Frequently Asked Questions on SAC Codes

SAC codes classify service offerings (e.g. 9983 for professional fees). Unlike HSN, SAC codes are standard across all services and are always 6 digits long. Verify that your service ledgers are mapped correctly to prevent GSTR-1 validation failures.

10. Mandatory 8-Digit HSN Codes for Customs Declarations

If your company engages in import and export transactions, you must report the complete 8-digit HSN code in all customs shipping bills and GSTR-1 returns. The 4-digit and 6-digit thresholds do not apply to foreign trade. Verify that your import/export item configurations in Tally Prime are updated to the full 8-digit code structure to avoid custom clearance delays.