Unused capital losses will only flow to a beneficiary's Schedule K-1 (Form 1041) in the final year. If it is not the final year, the capital losses are carried over on the fiduciary return until they can be applied to future capital gains, or until the final year when they may be distributed. 

See the IRS Instructions for Form 1041 and Schedules A, B, G, J, and K-1 for details.

Note that any link in the information above is updated each year automatically and will take you to the most recent version of the document at the time it is accessed.