Insert excerpt
Some Rate Differentials apply to the characteristics of an individual piece of equipment. For example, if a boat swapped into the Tow has a higher-horsepower engine than the one originally under the contract, a premium might be charged for this boat. This would be handled via a rate differential attached to the boat when it is added to the voyage.
Another type of Rate Differential could include additional daily charges for traveling west of Corpus Christi or east of New Orleans. This would be handled on the Activity Log - Barging, since these are typically included in the traffic reports provided by the owners.
In the Data Center 
, under Charter Party Terms, click Equipment Hire Rate Differentials.
...
The names of the Rate Differentials and their user-defined Bill codes appear.
The Subcode must match a code in the Operations Ledger.
The Subcode is used in Equipment Contracts when you make Hire Payments or when you issue a bill to a charterer.