Page type: primary-anchored (mirrors Uniform Network Code)

Uniform Network Code (UNC)

The UNC is the foundational industry code for GB gas transportation. It is a multi-party contract between all licensed Gas Transporters and all licensed Gas Shippers, setting out the commercial rights and responsibilities of all providers and users of the gas transportation system. Administered by the Joint Office of Gas Transporters.

Current version: 6.23 (25 March 2026) Legal basis: Gas Act 1986, s.7B; Gas Transporter Licence SSC A11 Code administrator: Joint Office of Gas Transporters Source file: sources/joint-office/unc.md Canonical URL: https://www.gasgovernance.co.uk/UNC

What the UNC does

The UNC creates a level playing field for gas transportation in GB by: - Defining how shippers access the gas pipeline network (capacity booking, nominations, balancing) - Setting the rules for gas balancing (ensuring supply matches demand each day) - Establishing the charging framework (how transporters recover their costs) - Governing supply point administration (how customers are registered and switched) - Managing the interfaces between different gas networks (NTS to distribution, interconnectors)

Structure

The UNC comprises five component documents:

1. General Terms (GT)

Foundational provisions: defined terms (GTC 1), interpretation rules (GTC 2), time conventions (GTC 2.2), dispute resolution (GTA), CDSP/UK Link specifications (GTD), and the Modification Rules for changing the code. The gas "Day" runs 05:00 to 05:00 (GTC 2.2.1(a)), distinct from the midnight-midnight electricity settlement period.

2. Transportation Principal Document (TPD)

The main body of the code. 21 active sections covering every aspect of gas transportation:

• System access and capacity (Sections A-B): System classification and the four classes of System Capacity -- NTS Entry, NTS Exit (Flat and Flexibility), LDZ, and Supply Point (TPD B1.2.2). Capacity is expressed in kWh/Day (TPD B1.2.9). Users who flow gas without holding capacity face Overrun Charges (TPD B1.3.1).
• Nominations and balancing (Sections C-F): How shippers nominate gas flows, how daily imbalances are calculated, how the System Operator (National Gas Transmission) balances the system residually, and how balancing costs are neutralised across shippers.
• Supply points and metering (Sections G, M): Supply point registration, shipper nomination, switching (now integrated with CSS/Retail Energy Code), and metering standards.
• Demand and planning (Sections H, O): Demand estimation algorithms (particularly for non-daily-metered sites), system planning, and the Long Term Development Statement.
• Entry and exit (Sections I, J): Gas quality specifications for system entry, and exit capacity arrangements including NTS offtake provisions.
• Operations (Sections K, L, N, Q): Operating margins, maintenance planning, shrinkage accounting, and emergency procedures (Network Gas Supply Emergency).
• Storage (Section R): NTS LNG storage facilities.
• Commercial (Sections S, V, X, Y): Invoicing and payment, general provisions (confidentiality, liability, force majeure), energy balancing credit management, and the charging methodologies (NTS in Part A-I, DN in Part B of Section Y).

3. Offtake Arrangements Document (OAD)

14 sections (A-N) governing the connections between different gas networks -- primarily the interface between National Gas Transmission (NTS) and the Distribution Network Operators (DNOs). Covers connection facilities, measurements, calorific value determination, telemetry, maintenance, operational flows, and cost recovery.

4. European Interconnection Document (EID)

5 sections governing interconnection points linking GB gas networks with European systems (Netherlands, Belgium, Ireland) via sub-sea pipelines. Covers capacity allocation, nominations, allocation, and incremental capacity release.

5. Independent Gas Transporter Arrangements Document (IGTAD)

Governs the interface between independent gas transporters and the main gas networks. Managed by the IGTAD Sub-Committee.

Key concepts

Capacity classes (TPD B1.2)

• NTS Entry Capacity: capacity to deliver gas into the NTS at Aggregate System Entry Points
• NTS Exit (Flat) Capacity: capacity to offtake gas from the NTS at an even rate across a Day
• NTS Exit (Flexibility) Capacity: capacity for DNO Users only, allowing uneven within-day offtake profiles
• LDZ Capacity: capacity at LDZ System Exit Points
• Supply Point Capacity: capacity at individual LDZ Supply Points, limited by feasible offtake rate (TPD B1.2.6)

Charging structure (TPD B1.7)

• Capacity Charges: fixed charges based on registered capacity at System Points (TPD B1.7.2)
• Commodity Charges: variable charges based on quantity of gas flow (TPD B1.7.3)
• Customer Charges: per-supply-point charges with three components -- Capacity Variable, Commodity Variable, and Fixed (TPD B1.7.4-1.7.5)
• CSEP Charges: for Connected System Exit Point users (TPD B1.7.7)
• Transmission Services Revenue Recovery Charges: recover allowed transmission revenue per the NTS Transportation Charging Methodology (TPD B1.7.8)
• Overrun Charges are explicitly excluded from Transportation Charges (TPD B1.3.1, B1.7.1(a))

Time periods (GTC 2.2)

• Gas Day: 05:00 to 05:00 (GTC 2.2.1(a))
• Gas Year / Capacity Year: 1 October to 30 September (GTC 2.2.1(f), (i))
• Formula Year: 1 April to 31 March (GTC 2.2.1(k))
• Winter Period: 1 November to 30 April (GTC 2.2.1(h))

Authority approval (GTC 2.8)

The Condition A11(18) Approval mechanism allows GEMA to approve or disapprove certain Transporter decisions under the Code, ensuring they align with the relevant objectives in the Gas Transporter Licence (GTC 2.8.1-2.8.4).

Governance

Modifications are proposed as UNC Modifications, assessed by workgroups under the Joint Office, voted on by the UNC Modification Panel, and approved or rejected by GEMA. The Modification Rules are part of the General Terms. The UNC has been designated as a qualifying document under Schedule 12 of the Energy Act 2023, which will give NESO/ISOP new governance powers.

Key parties

Defined terms

See the source file for the full defined terms register (60+ terms captured from GTC and TPD Section B).

Cross-references

Character positions

(No character positions recorded yet.)

Last updated

2026-04-05 (initial build from two-pass ingest)