Cybersecurity Vendor Due Diligence: The Complete 2026 TPRM Checklist

Cybersecurity vendor due diligence is the structured process of evaluating a third-party vendor’s security posture, compliance status, and risk exposure before onboarding them — and continuously throughout the relationship. According to the 2026 KPMG Global TPRM Survey, organisations that perform structured vendor due diligence experience 47% fewer third-party-related incidents than those relying on self-attestation alone. Yet most vendor assessment programmes still rely on annual questionnaires that miss the questions that matter.

Here’s the definitive checklist — built not to tick boxes, but to expose real risk. Whether you’re assessing a Tier 1 critical supplier or a new SaaS tool, these are the domains your due diligence must cover in 2026.