As part of "PTMeXchange", a project funded by BBSRC/NSF to improve sharing and deposition of high-quality sets of post-translational modifications (PTMs), a set of formats to encode post-translational modification (PTM) results are being developed. These are intended to be as simple as possible while still encoding sufficient information to properly evaluate FDR values and provide transparent validation information such that the results can be filtered to have low false positives and be transferred to knowledge bases such as UniProtKB. The set of formats is envisioned to include a PSM-level format, a peptidoform-level format, and a site-level format. The design is in progress with initial drafts already available, and further participation from the community is welcome.