working papers is a noun meaning "records kept of activities involved in carrying out a project". It carries 2 recorded senses.
records kept of activities involved in carrying out a project
“the auditor was required to produce his working papers”
a legal document giving information required for employment of certain people in certain countries
Definitions, synonyms and semantic relations for working papers come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.