Signature data for military platforms is critical in applications relevant to the Swedish Armed Forces, such as electronic warfare, duel simulations or evaluation of new acquisitions. The purpose of this report is to present activities and results during 2023- 2025 for the project Signature Modelling - part of the Swedish Armed Forces R&D programme for Sensors and low observables (FoT SoS, AT.9220425). The goal is to improve skills and capabilities benefitting applied projects in modelling signatures of specific, often operational or near operational platforms. Examples of research within IR modelling include re-establishing activities in marine IR modelling after being deprioritised since 2016. Missile plume modelling was developed through participation in a NATO group, and tested in the project TK Luft with good results. FOI also participated in studying the contributions of aluminium oxide to the plume. Examples of research within radar modelling include development and validation of signature computations for radomes - an important and challenging problem. Furthermore, the contribution of plasma was investigated, with relevance to hypersonic threats. It is important to continue to develop, improve, and extend the computational capabilities for both IR and radar. This refers both to improved methods, as well as increased complexity of the simulated systems.