The board set the firm transportation toll from Empress, Alta., to Dawn, Ont., at $1.42/GJ, compared with a 2013 toll of $2.58/GJ.
"The board approved multi-year fixed tolls that are competitive and provide TransCanada with a reasonable opportunity to recover its Mainline costs, given the increase in Mainline throughput that is forecast," the board said in a statement.
"These fixed tolls also provide toll certainty and stability to shippers and better allow the Mainline to compete."
The tolls are expected to remain in effect through 2017.
In approving the toll, the regulator also set the pipeline's return on equity at 11.5 per cent on a 40 per cent equity ratio and an incentive mechanism that would increase profits if annual net revenues are higher than forecast.
The NEB also approved several changes sought by TransCanada including proposed changes to the Mainline’s cost allocation, and the elimination of toll zones and the elimination of the risk alleviation mechanism.
However, the regulator also denied a number of other proposals by the company, citing that they resulted in "inappropriate cost shifting."
TransCanada noted that it viewed the rejected proposals as "fundamental concepts."
"This is a long and complex decision and we will need time to complete a full analysis before we can comment any further on how this decision will impact TransCanada," the company said in a statement.