Referring to the Indonesian Ministry of Energy and Mineral Resources (MEMR) Decree No. 15 of 2018 concerning Post-Operation Activities in Upstream Oil and Gas Businesses and the SKK Migas Working Guideline No. 040 (PTK 040) Revision 01 on the Abandonment and Site Restoration (ASR), all Production Sharing Contract (PSC) contractors in Indonesia are required to carry out the ASR operations when production ceases, and to establish and contribute to an ASR fund. Prior to carry out the ASR operations, PSC contractors must submit an ASR program plan and cost estimate to SKK Migas for approval. As a mature oil and gas field of which its offshore platforms were mostly installed in the 1970’s and 1980’s, PT. Pertamina Hulu Energi Offshore North West Java (PHE ONWJ) must be ready to face challenges regarding ASR operations and platform decommissioning. It is anticipated that during the strategic planning phase, PHE ONWJ will deal with many uncertainties and unknowns, including the asset integrity of inactive platform during idle time prior to decommissioning execution, which may lead to high decommissioning cost. Inactive platforms tend to get low priority in annual Inspection, Maintenance and Repair (IMR) activities. Meanwhile, the availability and quality of asset integrity data is crucial to reduce the uncertainties and to identify the unknowns. This paper mainly discusses the efforts to initiate the IMR strategy for inactive platforms in PHE ONWJ. An optimum IMR strategy for inactive platform in ONWJ field has been developed to ensure the availability and quality of the data as feeds for decommissioning projects. With comprehensive data, it is expected that PHE ONWJ can suppress the uncertainties, identify the unknowns, and optimize the decommissioning project costs.