UQC (Unit Quantity Code) in GST: List and Usage

UQC in GST is the Unit Quantity Code: a standard three-letter code for the unit in which a quantity is stated — PCS for pieces, KGS for kilograms, LTR for litres. It looks like a minor field, but it appears in the HSN summary of GSTR-1, on every e-invoice line and on the e-way bill, and a wrong or inconsistent code causes mismatches and rejections. This guide explains what UQC is, lists the common codes, and shows how to pick and map them.

What UQC is

Every GST document that carries a quantity also needs to say what the quantity is measured in. Free-text units — "pcs", "Nos.", "kg", "Kgs", "box of 12" — cannot be added up or compared across businesses, so GST systems use a fixed list of codes instead. Each code is three letters and stands for one unit: grammes, kilograms, metres, pieces, pairs, dozens, and so on. That code is the UQC.

UQC sits alongside the HSN code. The HSN code says what the goods are; the UQC says how the quantity is counted. Together with the quantity and value they describe a line of supply in a form the department can aggregate.

Where UQC is used

• GSTR-1 HSN summary. The HSN-wise summary of outward supplies reports quantity against a UQC for each HSN code. See the GSTR-1 filing guide and the HSN digit rules by turnover.
• E-invoice. Each item line in the e-invoice JSON carries a unit, which is validated against the UQC master of the e-invoice system.
• E-way bill. The goods details in Part A include quantity and unit, again from the UQC list. See e-way bill Part A and Part B.
• Tax invoice. The invoice itself states quantity and unit for goods; using the UQC there too keeps everything aligned. See the GST invoice format.

Common UQC codes

The table below covers the codes most businesses need. The full official list is published on the GST portal and in the masters of the e-invoice system; treat that as the source of truth.

Why the right UQC matters

HSN summary mismatches. The HSN summary is grouped by HSN code and UQC. If the same item is invoiced as PCS on some bills and NOS on others, it shows up as two lines, and the total quantity for that HSN code is split. Where e-invoice data flows into GSTR-1, the auto-populated HSN figures carry whatever units your invoices used, so inconsistencies in billing surface at filing time.

E-invoice validation. The IRP validates each item's unit against its UQC master. A unit that is not on the list — a typo, a lower-case variant, an ERP's own abbreviation — can get the request rejected, and the invoice has no IRN until it is fixed. This is one of the more common schema errors when integrating billing software; see e-invoicing integration with billing software.

Consistency across documents. The invoice, the e-way bill and the return describe the same supply. If they use different units for the same goods, reconciling them later, or explaining them to an officer, takes more work than it should.

How to choose the right UQC

1. Use the unit you actually sell in. If the invoice quantity is "10" and you mean ten cartons, the UQC is CTN, not PCS.
2. Match the quantity to the code. Selling 2.5 kilograms of spices is KGS with quantity 2.5, not GMS with 2.5.
3. Pick one code per item and keep it. For countable goods, PCS, NOS and UNT are all acceptable; choose one and use it everywhere for that item.
4. Prefer a specific code to a generic one. PRS for footwear, SQM or SQF for tiles, MTR for fabric.
5. Check the official list before using OTH.

If you are still settling the HSN code itself, start with how to search for an HSN code; the unit usually follows naturally from how the goods are traded.

UQC for services

Services do not have a physical quantity, so for services the quantity and unit are generally not meaningful. Service lines are identified by their SAC code, and the value of the service is what matters for tax. Follow what the current GSTR-1 HSN table and the e-invoice schema accept for service lines rather than inventing a unit; where a unit must be given and nothing on the list fits, OTH is the usual fallback. Your billing software should handle service lines separately from goods rather than forcing a goods unit onto them.

Mapping ERP units to UQC

Most ERPs and billing tools let you define your own units: "Pcs", "Nos.", "Kg", "Box-12". These are fine for internal use, but every one of them needs to map to an official UQC before it reaches an e-invoice, e-way bill or return. The practical approach:

• add a UQC field to the unit master (or the item master) and fill it once for every unit;
• map aliases to the same code — "Pcs", "pc" and "Piece" all become PCS;
• map pack units to the pack code, not the contents — "Box-12" becomes BOX, and the quantity is the number of boxes;
• block unmapped units at invoice creation, so a bad unit is caught before the IRN request, not after;
• review the HSN summary before filing for the same HSN code appearing under more than one UQC.

Frequently asked questions