This practitioner guide addresses the challenge HR professionals face when evaluating and selecting performance management software (PMS). The author's central argument is that standard vendor demos and feature checklists are insufficient for identifying how a platform performs under real operational conditions — such as mid-year reorganizations, performance improvement plan (PIP) documentation, and cross-manager rating calibration. The article presents 16 categorized vendor questions across six domains — scope and fit, goals and reviews, HR oversight, data and integration, manager and employee experience, and implementation and cost — each accompanied by two follow-up questions. Key evidence is drawn from practitioner reasoning rather than empirical sources, with the author identifying common failure points such as documentation gaps, upsell-hidden features, and calibration inconsistencies. The article concludes with a vendor comparison checklist emphasizing workflow validation, multi-year pricing, and HRIS integration. The implications drawn are that poorly selected PMS tools expose organizations to legal risk, pay inequities, and audit vulnerabilities, while a rigorous vendor evaluation process reduces downstream problems during merit cycles or employment disputes. Key insights: Performance management software selection failures often stem from feature-level evaluation rather than workflow-level stress testing, particularly around PIP documentation, calibration sessions, and mid-year goal changes. A significant risk in PMS procurement is pricing opacity — features assumed to be core functionality frequently require paid upgrades, and costs tend to escalate with headcount growth. HR oversight mechanisms within PMS platforms vary substantially: some systems surface manager non-compliance through dashboards while others require manual custom reporting, creating gaps in documentation accountability. Practical takeaways: HR teams evaluating PMS vendors can use a structured question grid across six domains — scope, goals and reviews, oversight, data integration, user experience, and implementation — to compare vendor responses systematically during demos and reference calls. Validating three-year total cost of ownership, including add-on modules and user growth pricing, is identified as a critical step before contract signing to avoid post-launch budget exposure.