  The High Energy Phyiscs community has developed and needs to maintain many
tens of millions of lines of code and to integrate effectively the work of
thousands of developers across large collaborations. Software needs to be
built, validated, and deployed across hundreds of sites. Software also has a
lifetime of many years, frequently beyond that of the original developer, it
must be developed with sustainability in mind. Adequate recognition of software
development as a critical task in the HEP community needs to be fostered and an
appropriate publication and citation strategy needs to be developed. As part of
the HEP Softare Foundation's Community White Paper process a working group on
Software Development, Deployment and Validation was formed to examine all of
these issues, identify best practice and to formulare recommendations for the
next decade. Its report is presented here.
