According to the TNC in case when gas is delivered to:

• entry point at interconnection with domestic natural gas fields, nitrogen removal plants or natural gas mixing facilities,
• exit point to the ISO's system or directly to the final Customer under more than one transmission contract,

the operator of the installation connected/ISO/final Customer shall perform the allocation of the quantities of gaseous fuel delivered to such entry/exit points to individual Shippers active at the entry/exit points.

Operative and settlement allocations should be sent to the Transmission System Operator via Information Exchange System (IES) 

For more information on allocations you will find below:

• Obligation to allocate
• Operative allocations
• Settlement allocations
• Operative allocation performance timeline
• MARSIT messeges