What Is Vendor Due Diligence? Process, Checklist & Best Practices

Third-party vendors can give your business access to critical technology, expertise, and services, but they can also introduce security, compliance, privacy, and operational risks. The more vendors your organization relies on, the more important it becomes to understand those risks before granting access to sensitive data or business-critical systems.

Vendor due diligence gives teams a structured way to evaluate those risks before onboarding and throughout the relationship. An effective process goes beyond questionnaires and certifications to assess controls, compliance evidence, privacy practices, and overall risk. In this article, we’ll explain what vendor due diligence is, walk through the process, and provide a practical checklist and best practices for effective vendor reviews.

What is vendor due diligence?

Vendor due diligence is the process of evaluating a third party’s security, compliance, privacy, financial, and operational risks before entering into or expanding a business relationship.

Organizations working with cloud providers, software vendors, contractors, service partners, or data processors should have a formal due diligence process. The depth of the review should reflect the vendor’s risk level, including the data they handle, the systems they can access, and how critical their services are to business operations.

A consistent process helps identify security weaknesses, compliance gaps, and operational risks before they affect the business. It also creates a documented basis for vendor approval and remediation decisions, while supporting regulatory compliance and ongoing third-party risk management (TPRM) throughout the vendor relationship.

The vendor due diligence process: Step-by-step

A strong vendor due diligence process follows a clear sequence, from assessing risk to making a documented decision. The level of review should reflect the vendor’s access, data exposure, business criticality, and compliance impact. Here are the key vendor due diligence steps:

Step 1: Tier vendors by risk

Start by determining how much risk the vendor could introduce based on the systems it can access, the data it handles, and how critical its services are to your operations. Consider different types of vendor risk, including security, privacy, operational, financial, and compliance risk, to assign an appropriate risk tier and level of review.

Step 2: Define review requirements

Based on the vendor’s risk tier, determine what evidence, reviews, and approvals are required, such as security questionnaires, compliance reports, penetration test results, or privacy assessments. These requirements should align with your TPRM policy to keep reviews consistent across vendors.

Step 3: Collect vendor documentation

Gather the documentation needed to evaluate the vendor, such as SOC 2 reports, ISO certifications, security questionnaires, privacy policies, DPAs, business continuity plans, and penetration test summaries. The amount of evidence requested should reflect the vendor’s risk, with more extensive documentation required for critical third parties.

Step 4: Review security and compliance posture

Review the evidence to determine whether the vendor’s controls meet your security and compliance requirements, including areas such as access control, encryption, vulnerability management, incident response, and business continuity. A formal vendor risk assessment can help identify and document the specific risks the vendor presents.

Step 5: Assess legal, privacy, and commercial terms

Review contractual requirements such as data processing, breach notification, audit rights, SLAs, liability, data retention, and termination obligations. For vendors handling personal or regulated data, confirm that their privacy commitments align with internal policies, customer agreements, and applicable requirements.

Step 6: Document findings and remediation

Record any control gaps, unanswered questions, compensating controls, remediation requirements, and residual risks identified during the review. For issues that do not prevent onboarding, assign an owner and remediation timeline so they can be tracked as part of the broader TPRM program.

Step 7: Make the onboarding decision

Use the findings to approve the vendor, approve it with conditions, defer onboarding until remediation is complete, or reject the relationship. Establish who owns the vendor relationship and when reassessment is required, while AI TPRM can help connect approvals, evidence, remediation, and ongoing monitoring in one workflow.

7 steps in the vendor due diligence process 

Step	Primary goal	Typical outputs	Key owner
Tier vendors by risk	Match review depth to exposure	Risk tier, intake record, review path	Security or procurement
Define review requirements	Set evidence and approval needs	Required documents, stakeholder list	Compliance or TPRM lead
Collect vendor documentation	Gather evidence for review	Reports, questionnaires, contracts	Vendor owner
Review security and compliance posture	Evaluate controls and risk	Findings, risk notes, control gaps	Security and compliance
Assess legal, privacy, and commercial terms	Confirm contractual protection	DPA review, legal comments, SLA notes	Legal and privacy
Document findings and remediation	Record gaps and required actions	Risk register entry, remediation plan	TPRM or compliance
Make the onboarding decision	Determine whether to proceed	Final decision, conditions, reassessment date	Business owner and approvers

Vendor due diligence checklist

A practical vendor due diligence checklist helps teams evaluate third parties consistently across key risk areas. The depth of each review should reflect the vendor’s risk tier, data access, and importance to business operations. Here is the vendor due diligence checklist:

Security controls

Review the security controls relevant to how your organization will use the vendor, including access management, MFA, encryption, vulnerability management, monitoring, and incident response. The level of scrutiny should reflect the vendor’s access and potential impact. Vendors handling sensitive data or accessing production systems should require stronger evidence than lower-risk tools.

Compliance evidence

Review relevant evidence such as SOC 2 reports, ISO 27001 certifications, security policies, and audit reports. Confirm that each document is current and covers the service or environment your organization will use. For organizations focused on continuous compliance, also consider whether vendor evidence can be kept current between formal review cycles.

Privacy posture

Determine what personal or sensitive data the vendor collects, processes, stores, or accesses, including where it is stored and how long it is retained. Identify subprocessors and any cross-border data transfers that could introduce additional requirements. Review DPAs, breach notification procedures, deletion practices, and other relevant privacy protections.

Legal terms

Review contractual protections covering confidentiality, security obligations, breach notification, audit rights, SLAs, liability, and data ownership. Pay particular attention to what happens during an incident or when the relationship ends. Confirm requirements for data return or deletion, termination, and ongoing responsibilities.

Operational resilience

Assess whether the vendor can continue providing its services during outages, security incidents, or other disruptions. Review business continuity, disaster recovery, backups, uptime commitments, and escalation processes. For critical vendors, consider recovery objectives and dependencies that could affect your own operations.

Financial viability

Consider whether the vendor has the financial and operational stability to support the relationship over time. Depending on its importance, review factors such as financial information, insurance coverage, ownership changes, and ability to scale. For difficult-to-replace vendors, also consider concentration risk and the availability of alternative providers.

Intake and scoping

Create a clear intake record covering the service, business owner, data involved, integrations, and required system access. Use this information to determine which areas require deeper review and identify the types of vendor risk involved. Vendor risk management solutions can help centralize this information and ensure each third party is assessed based on its actual risk.

Evidence validation

Verify that submitted evidence is current, complete, and relevant to the specific service being assessed. Check report dates, scope, exclusions, findings, exceptions, and remediation status before accepting documentation. For example, an outdated penetration test or SOC 2 report covering a different service may provide limited assurance.

Risk disposition

Give every issue identified during due diligence a clear outcome, whether it is accepted, remediated, managed through compensating controls, or escalated. Document the finding, required action, owner, deadline, and final decision. This creates a clear audit trail and supports consistent decisions across the broader TPRM process.

Vendor due diligence best practices

Effective vendor due diligence goes beyond completing a checklist before procurement. Strong programs use consistent processes, clear ownership, risk-based reviews, and ongoing monitoring throughout the vendor relationship. Here are the vendor due diligence best practices:

Standardize review paths

Create standardized review paths based on vendor risk, required evidence, stakeholders, and escalation rules. These should align with your third-party risk management policy so teams have a consistent process for assessing and approving vendors.

Standardization also reduces delays and improves audit readiness. Instead of deciding what to request for every vendor, teams can focus on reviewing evidence, documenting findings, and addressing risk.

Match due diligence to vendor risk

Avoid applying the same level of due diligence to every third party. Review depth should reflect factors such as data sensitivity, system access, regulatory exposure, business criticality, and the potential impact of an incident.

A risk-based approach focuses resources where they matter most. Lower-risk vendors can follow a lighter review, while critical vendors receive deeper security, privacy, compliance, legal, and operational assessments.

Treat due diligence as an ongoing program

Vendor due diligence should be part of a broader TPRM program that continues after onboarding. Periodic reassessments and trigger-based reviews help teams respond when a vendor’s services, controls, subprocessors, or data practices change.

Set reassessment schedules based on vendor risk and define triggers for earlier reviews, such as security incidents, new system access, or significant service changes. TPRM software can help centralize these reviews, track changes, and keep vendor risk information current over time.

Align business and control owners

Vendor due diligence should involve the relevant business owners, procurement, legal, privacy, security, and compliance teams. Each stakeholder contributes different information and expertise to the final decision.

Define who owns each stage, approves exceptions, and manages remediation. Clear responsibilities reduce delays and prevent important issues from getting lost between teams.

Validate evidence, not just its existence

A SOC 2 report, ISO certification, or penetration test does not automatically mean a vendor meets your requirements. Check the scope, dates, findings, exceptions, and remediation status to confirm the evidence applies to the service you will use.

The same applies to questionnaires and other vendor-provided documentation. For higher-risk vendors and critical controls, verify responses against supporting evidence where appropriate.

Track remediation through completion 

Not every gap needs to prevent vendor approval, but every meaningful issue should have a clear outcome. Document whether it requires remediation, compensating controls, formal risk acceptance, or prevents onboarding.

Assign owners and deadlines to remediation items and track them through completion. This creates an audit trail and prevents identified risks from being forgotten after approval.

Use automation where review volume is high

Manual processes become harder to manage as vendor numbers, questionnaires, documents, and reassessments grow. Automation can help collect evidence, route approvals, track remediation, and manage reassessment schedules.

Dedicated vendor risk management workflows can keep evidence, findings, approvals, and monitoring connected in one place. This reduces administrative work and provides clearer visibility across the vendor due diligence process.

How long does vendor due diligence take?

The time required for third-party due diligence varies depending on the vendor’s risk level, the complexity of the service, and the depth of review required. A low-risk vendor with limited access to sensitive data may move through the process relatively quickly, while a critical vendor handling sensitive information or accessing core systems typically requires a more extensive security, compliance, privacy, and legal review.

Evidence quality and internal coordination can also affect the timeline. Effective vendor compliance management helps keep questionnaires, compliance reports, documentation, approvals, and remediation organized, reducing delays caused by missing evidence, unclear ownership, or unresolved gaps.

A risk-based process can help prevent unnecessary delays. By establishing vendor tiers and matching review requirements to each level of risk, teams can move routine vendors through a lighter process while dedicating more attention to higher-risk relationships. Clear ownership, standardized workflows, and centralized evidence also help teams set more realistic review timelines and avoid preventable bottlenecks.

How Scytale simplifies vendor due diligence

Scytale brings vendor due diligence into one centralized workflow, automating evidence collection, questionnaire reviews, remediation, and approvals. Teams can keep vendor documents, findings, and risk status in one place while connecting reviews to broader third-party risk management. Scytale’s agentic GRC ecosystem also supports evidence review and cross-framework mapping across 80+ frameworks, helping teams apply consistent requirements based on vendor risk.

Scytale also pairs automation with dedicated GRC experts who help teams navigate requirements, review gaps, and strengthen their vendor risk processes. This combination reduces manual coordination, keeps remediation and supporting documentation organized, and creates a clearer audit trail from initial review through ongoing oversight. 

FAQs about vendor due diligence