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GST state codes

GST state code 18: Assam

Assam's GST state code is 18, the last of the north-eastern codes. Tea from Dibrugarh, muga silk from Sualkuchi and the trade through Guwahati all run on GSTINs that start with 18.

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In short

Assam has GST state code 18, so every GSTIN registered there begins with 18. A local sale carries CGST and SGST; a sale to West Bengal carries IGST. SimpleERP reads 18 from the buyer's GSTIN and picks the tax.

Illustration of GST tax invoice INV-2026-27-0213 to Ravi Stores with CGST 9% and SGST 9%, round off, a UPI QR code and the amount in words.

The data

GST state code 18 at a glance

FieldValue
State code18
GSTIN prefix18 (the first two characters)
Tax on a local saleSGST, with CGST
Union territoryNo, a state
Professional taxYes
Nearby states and codesWest Bengal (19), Meghalaya (17), Arunachal Pradesh (12)
Sample GSTIN (fictional)18AAACL1234A1Z8
Assam at a glance, as notified; check the GST portal.

Sources: GST portal: state code list (GSTIN format), Assam: professional tax (state tax department). Verified .

What the code 18 means on a GSTIN

A GSTIN has 15 characters. Take the sample 18AAACL1234A1Z8, a made-up number with a valid check character. 18 is the state code for Assam. AAACL1234A is the PAN of the business, and 1 says this is the first registration under that PAN in Assam. Z is the same on almost every GSTIN, while 8 is a check character worked out from the first 14, so a single wrong digit in 18AAACL1234A1Z8 fails the check.

Guwahati is the gateway for goods into the whole north-east, so an Assam distributor often sells across five or six state borders. A sale to Shillong (17), Itanagar (12) or Dimapur (13) carries IGST. Only buyers whose GSTIN also starts with 18 get CGST and SGST.

Intra-state or inter-state: which tax applies when the supplier is in Assam?

When a Dibrugarh tea estate sells chests to a packer in Guwahati, supplier and place of supply are both in Assam, so the invoice carries CGST and SGST. When the estate ships to a blender in Kolkata, the place of supply moves to West Bengal and the whole tax becomes IGST; the same holds when the estate supplies a hotel in Port Blair, because Andaman and Nicobar Islands has its own code, 35.

SalePlace of supplyTax at 18%Tax on ₹4,50,000
A Dibrugarh tea estate sells chests to a packer in GuwahatiAssam (18)CGST 9% + SGST 9%₹40,500 + ₹40,500
The estate ships to a blender in KolkataWest Bengal (19)IGST 18%₹81,000
The estate supplies a hotel in Port BlairAndaman and Nicobar Islands (35)IGST 18%₹81,000
Assumes an 18% rate on a taxable value of ₹4,50,000 for Assam; rates change, so confirm yours with your CA or the GST portal.

Does professional tax apply in Assam?

Yes. Assam levies professional tax on salaries, as notified; check the current slabs with the Assam tax department before you deduct it, since this page lists no Assam slab amounts. In SimpleERP payroll, Professional Tax is a fixed deduction on the payslip that starts at zero, so you enter the Assam amount once.

How SimpleERP reads the state from a GSTIN

You never type 18 or Assam on an invoice: SimpleERP takes both from the customer's GSTIN and works out the rest.

  • The state fills from the first two characters of the GSTIN: type 18AAACL1234A1Z8 and SimpleERP shows Assam (18) under the field, after checking the last character.
  • The place of supply comes from the buyer's GSTIN, so a West Bengal buyer fills West Bengal (19); a buyer without a GSTIN gets the state picked once on the customer record.
  • Each invoice line compares the place of supply with your Assam branch and carries CGST and SGST, or IGST.

Illustration of the keyboard-first invoice editor with a focused line, live tax totals and shortcut hints.

For a Assam branch, the billing editor picks CGST and SGST or IGST per line from the place of supply.

Sources

FAQ

Questions, answered

What is the GST state code for Assam?

Assam uses GST state code 18. Every GSTIN registered in Assam, from Guwahati to Dibrugarh and Silchar, starts with 18. The north-eastern states run from Sikkim at 11 to Assam at 18.

Is code 18 used for SGST or UTGST?

SGST. Assam is a state, so a sale within Assam carries CGST and SGST at half the rate each. UTGST is for union territories without a legislature and does not apply to any of the north-eastern states.

Which code do I use for a customer in Assam?

The buyer's GSTIN tells you: 18 for Assam, 19 for a blender in Kolkata, 17 for a buyer in Shillong. For a buyer without a GSTIN, use the state where the goods are delivered.

Does SimpleERP need me to pick Assam by hand?

No. A Guwahati distributor using SimpleERP types each buyer's GSTIN once; the state fills from the first two characters, and every invoice line then carries CGST and SGST or IGST to match. Buyers without a GSTIN get their state picked on the customer record.

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