When a retailer asks you to encode RFID tags "as SGTIN-96", it can sound intimidating. In reality it is a well-defined, logical way of turning the barcode number you already use - the GTIN - into a number that is unique for every single item. Understanding how it works helps you avoid the encoding mistakes that cause shipment problems.

From GTIN to serialised item

A GTIN (the number behind an EAN-13 or UPC barcode) identifies a product: for example, a navy T-shirt in size M. Every navy size M T-shirt shares the same GTIN. RFID adds a serial number, so each individual T-shirt gets its own identity. The combination is called an SGTIN - Serialised Global Trade Item Number.

SGTIN-96 is the 96-bit binary encoding of that SGTIN, defined in the GS1 EPC Tag Data Standard, and written into the EPC memory bank of an EPC Gen2 (ISO/IEC 18000-63) UHF tag.

The six fields of SGTIN-96

1. Header (8 bits) - identifies the scheme. For SGTIN-96 the header value is 0x30, which is why these EPCs start with "30" in hexadecimal.
2. Filter value (3 bits) - tells readers what kind of object this is, for example a point-of-sale item or a case. Your buyer will specify the value to use.
3. Partition (3 bits) - indicates how the next 44 bits are split between company prefix and item reference, because GS1 company prefixes vary in length.
4. Company prefix (20-40 bits) - your GS1 company prefix, taken from the GTIN.
5. Item reference (24-4 bits) - the remaining product part of the GTIN, including the indicator digit. The GTIN check digit is not encoded; it is recalculated when decoding.
6. Serial number (38 bits) - a numeric serial unique within that GTIN, giving a very large range of possible values.

Encoding software handles the binary conversion. What you need to control is the input: the correct GTIN, the correct filter value and a serial number that has never been used before for that GTIN.

Why serial number management matters

The single most important rule is: never issue the same serial number twice for the same GTIN. Duplicate EPCs confuse inventory systems, because two physical items appear as one. Common causes of duplicates include:

• Two printers or two factories encoding the same GTIN from the same starting serial.
• Re-running a print job after a jam without adjusting the serial counter.
• Resetting software or reinstalling a printer driver that held the counter.
• Manual spreadsheets copied between orders.

Retail programmes often solve this by assigning serial ranges to each supplier or each printing location, or by having a central service issue EPCs. Follow whatever method your buyer prescribes.

Other memory banks on a Gen2 tag

An EPC Gen2 tag has four memory banks:

• Reserved - stores access and kill passwords.
• EPC - holds the SGTIN-96 (or other EPC) plus control bits.
• TID - a factory-programmed tag identifier, including chip model and often a unique serial, which cannot be changed.
• User - optional extra memory on some chips.

Some buyers ask suppliers to lock the EPC memory after encoding, or to record the TID along with the EPC for authentication purposes. Check the specification carefully.

Verifying your encoding

Before shipping, read a sample of tags and decode them back to GTIN and serial. Confirm that:

• The header is 30 (SGTIN-96).
• The decoded GTIN matches the printed barcode on the same tag.
• The filter value is the one requested.
• Serials are unique and within any assigned range.

A mismatch between the printed barcode and the encoded EPC is one of the most common faults found in supplier audits, and it is easy to catch with a handheld reader and decoding software.

Other EPC schemes

SGTIN-96 is not the only option. SSCC-96 identifies logistics units like pallets, GRAI-96 is used for returnable assets, and GIAI-96 for fixed assets. There is also SGTIN-198, which allows alphanumeric serials. Use the scheme your trading partner specifies.

Need help with encoding?

Indian RFID can supply pre-encoded tags to your specification, or set up RFID printers and encoding software at your site. Our case studies show examples of encoding workflows we have implemented.

Share your buyer's encoding specification on WhatsApp +91-9717122688 or email gm@indianbarcode.com, and we will check it and suggest the simplest way to comply.

Contact Indian RFID

Indian RFID is the RFID arm of Mindware, which also delivers complete barcode solutions, barcode labels and the full range of Mynds brand barcode ribbons.

Phone / WhatsApp: +91-9717122688
Email: gm@indianbarcode.com
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