OASIS-D Guidance Manual - with OASIS-D1 2020 Update. OFFICIAL CMS FINAL PUBLICATION - CMS OASIS Guidance Manual, originally posted for OASIS-D, but now with OASIS-D1 update. Contains guidance to direct OASIS coding for assessments with M0090 date of January 1, 2020 through December 31, 2022. This manual is available from OASIS Answers in a convenient hard copy, with tab dividers and a sturdy binder for easy reference by your team. The OASIS Guidance Manual was developed by the Centers for Medicare & Medicaid Services (CMS) and its contractors and contains content most relevant for home health agencies’ efforts in implementing OASIS, with emphasis on item guidance.