You are required to issue a K-1 to report a beneficiary's share of the estate’s or trust’s income, credits, deductions, etc..
The distribution made in 2015 should be reported to the beneficiaries in 2015. Income items from 2015 must be distributed in 2015.
See
https://www.irs.gov/pub/irs-pdf/i1041sk1.pdf for guidance on what is included in the K-1. Turbo Tax will prepare K-1 forms as part of the Trust’s tax return.
See
http://taxmap.ntis.gov/taxmap/pubs/p559-004.htm for guidance on the treatment for the distribution of non-income items
