A template can be easy to customise, but the licence may distinguish a finished design from handing over the original files.
Open the licence that applies to the exact asset and check who can use it, for what purpose and whether the source files can be shared. Record the asset name and where you obtained it. Treat stock images, fonts and other bundled resources as separate items when they have separate terms.
Prepare the deliverables list before promising a handover. If a licence is unclear about client editing or reuse, ask the supplier for clarification. Keep a record of the terms that applied when the asset was acquired.