SA-9(3): Establish and Maintain Trust Relationship with Providers

To meet the sa-9(3): establish and maintain trust relationship with providers requirement, you must define what “trust” means for each external service provider, document the conditions that create that trust (contractual + technical + operational), and keep that trust current through periodic validation and change-driven reviews. The deliverable is a repeatable process with clear ownership and durable evidence.

Key takeaways:

• Define trust requirements by provider type, data sensitivity, and system criticality, then make them enforceable in contracts and configurations.
• Operate the relationship: continuous validation, change notifications, and re-assessments when the provider or your use changes.
• Audit success depends on evidence: documented trust criteria, approvals, monitoring outputs, and issue closure records.

SA-9(3) is an operator’s control. Assessors are not looking for philosophy about “trust”; they want to see how you decide a third party is trustworthy enough to host, process, transmit, or support your information system, and how you ensure that decision remains valid over time. The difference between “we did due diligence once” and “we maintain a trust relationship” is operational cadence: triggers, monitoring, governance, and re-authorization when conditions change.

This requirement shows up most sharply in cloud, managed security services, SaaS, hosting, payment processors, call centers, and any outsourced IT function where the third party’s people and systems become part of your security boundary. If you cannot clearly state (1) the conditions of trust, (2) where they are documented, (3) how they are verified, and (4) what happens when they fail, SA-9(3) will turn into a recurring audit finding.

The practical goal: a Trust Relationship Standard that is tied to procurement and onboarding, enforced through contract language and technical controls, and maintained through monitoring and periodic review. That is what lets a CCO, GRC lead, or system owner operationalize SA-9(3) quickly and defend it during an assessment.

Regulatory text

NIST requirement (SA-9(3)): “Establish, document, and maintain trust relationships with external service providers based on the following requirements, properties, factors, or conditions: {{ insert: param, sa-9.3_prm_1 }}.” ¹

What the operator must do:

1. Establish a trust relationship: decide what must be true before you rely on a provider (security, privacy, resilience, legal/contract, operational).
2. Document the trust relationship: record the criteria, the provider’s commitments, and your verification results in artifacts you can produce on demand.
3. Maintain the trust relationship: keep it current via periodic validation and event-driven reassessment when the provider or the service changes. ²

Because the parameter text is intentionally customizable in the control, your job is to define the “requirements, properties, factors, or conditions” that are appropriate for your environment, then prove you apply them consistently.

Plain-English interpretation

A third party is “trusted” only under explicit conditions. SA-9(3) requires you to:

• Set the trust conditions up front (before onboarding or before expanding scope).
• Make those conditions enforceable (contractual requirements + technical guardrails + operational expectations).
• Re-check trust continuously (monitoring, reviews, change management, and remediation).

If you cannot explain what would cause you to reduce scope, pause data flows, or exit the provider, you probably have not operationalized “maintain.”

Who it applies to

Entities

• Federal information systems and programs implementing NIST SP 800-53 controls. ²
• Contractors handling federal data or operating systems aligned to NIST SP 800-53 as a contractual requirement. ²

Operational context

• Any external service provider with access to your systems, data, or operational processes (cloud/IaaS, SaaS, MSP/MSSP, data processors, support vendors, outsourced development, hosting, identity providers).
• Highest priority where the third party:
  • Handles sensitive regulated data
  • Provides privileged access or admin tooling
  • Operates critical business services
  • Subcontracts meaningful portions of the service (fourth parties)

What you actually need to do (step-by-step)

1) Define “trust” as an implementable standard

Create a Trust Relationship Standard that lists required conditions by risk tier. Include:

• Security baseline expectations (access controls, encryption, logging, vulnerability management)
• Assurance evidence you accept (e.g., independent assessments, customer audit rights, control attestations)
• Operational expectations (incident notification, change notice, support SLAs, BCP/DR)
• Data handling rules (data location, retention, deletion, subcontractors)
• Termination/exit requirements (data return, secure deletion, transition support)

Operator tip: Write these as “must” statements that can be inserted into contracts and validated by evidence.

2) Classify providers and map trust requirements to each tier

Build a lightweight decision matrix:

• Tier factors: data sensitivity, connectivity, privilege level, criticality, substitutability, geographic/legal constraints.
• Outcome: required trust conditions (controls + contract clauses + monitoring depth).

Keep the matrix simple enough that procurement and engineering will actually use it.

3) Establish the trust relationship during intake and onboarding

For each provider in scope:

• Perform third-party due diligence against your trust standard.
• Document gaps, compensating controls, and risk acceptance decisions.
• Ensure contractual alignment (see next step).
• Confirm technical enforcement before go-live (SSO, least privilege, logging, network constraints, key management patterns appropriate to your architecture).

4) Encode trust conditions into contracts and security requirements

Your contract package should include, as applicable:

• Security requirements exhibit aligned to your trust standard
• Incident notification obligations and timelines that match your internal response needs
• Right-to-audit or right-to-assessment language (or acceptable alternatives)
• Subprocessor / subcontractor controls and notification
• Data ownership, use restrictions, retention, deletion, and exit support
• Service change notification (material changes to controls, hosting, or ownership)

Common hangup: Teams rely on “SOC 2 exists” as a substitute for contractual obligations. SA-9(3) expects you to define and maintain trust conditions; an attestation may support trust, but it rarely replaces contract enforceability.

5) Maintain trust with ongoing validation (recurring + event-driven)

Implement a provider trust maintenance workflow with two mechanisms:

A. Recurring validation

• Re-collect assurance evidence on a defined cadence appropriate to tier.
• Re-confirm access: active accounts, privileged roles, API tokens, service principals.
• Re-check data flows and storage locations.
• Reassess open issues and remediation status.

B. Event-driven reassessment triggers Reassess trust when any of these occur:

• Material security incident at the provider
• Significant service change (new subprocessor, region move, architecture change)
• Contract renewal or scope expansion (new data types, new integrations)
• Ownership change or major organizational restructure
• Repeated SLA failures that affect security or resilience expectations

6) Govern exceptions and failures of trust

Define what happens when trust conditions are not met:

• Severity-based response (restrict access, suspend integrations, require remediation plan, executive risk acceptance, terminate)
• Timelines for remediation commitments and follow-up validation
• Clear decision authority (system owner, security, legal, privacy, procurement)

This is where many programs fail: they collect risk findings but do not run them to closure or adjust access accordingly.

7) Make it assessable: assign ownership and evidence mapping

Assign:

• A control owner (typically Third-Party Risk / GRC)
• Operational owners for contract execution (Legal/Procurement) and technical enforcement (Security/IT)
• A single system of record for each provider’s trust package

If you use Daydream, the cleanest operational pattern is to map SA-9(3) to a control owner, embed the step-by-step procedure as the “how,” and schedule recurring evidence collection so audits become retrieval rather than archaeology.

Required evidence and artifacts to retain

Keep artifacts per provider, plus program-level artifacts.

Program-level

• Trust Relationship Standard (policy/standard)
• Provider tiering methodology and decision matrix
• Procedure/workflow for intake, approval, monitoring, and exception handling
• RACI showing who approves trust, who monitors, who can accept risk

Provider-level (trust package)

• Completed due diligence record against your trust standard
• Contract exhibits: security requirements, incident notification, audit/assessment rights, subprocessor terms, data handling, exit clauses
• Assurance evidence received and reviewed (and your review notes)
• Access reviews and results (including revocations)
• Monitoring outputs (alerts, scorecards, breach notifications, service health signals) where applicable
• Risk register entries, remediation plans, and closure proof
• Re-approval records for renewals, scope changes, and material events

Common exam/audit questions and hangups

Expect these questions:

• “Show me the criteria you use to decide a provider is trustworthy for this system.”
• “Where is the trust relationship documented for Provider X?”
• “How do you know the provider still meets the conditions you required at onboarding?”
• “What triggers a reassessment, and show an example where you executed it.”
• “How do contracts enforce incident notification, subcontractor control, and audit/assessment rights?”
• “Show evidence that access is restricted when trust conditions are not met.”

Hangups that cause findings:

• Criteria exist but are not tied to tiering and not consistently applied.
• Contracts are missing the clauses that operational teams assume are “standard.”
• Monitoring is informal (email threads) and not retained as evidence.
• Exceptions are approved verbally, with no compensating controls or expiry.

Frequent implementation mistakes and how to avoid them

1. Mistake: Treating “trust” as a one-time onboarding step.
   Fix: Define recurring validation and event-driven triggers, and record each cycle’s outputs.

2. Mistake: Confusing “provider has a report” with “provider meets our conditions.”
   Fix: Map your trust standard requirements to the provider’s evidence and document gaps explicitly.

3. Mistake: No linkage between contracting and technical enforcement.
   Fix: Require a go-live checklist that includes both executed contract artifacts and technical guardrails (SSO, least privilege, logging).

4. Mistake: No consequence model for broken trust.
   Fix: Document escalation paths and pre-approved actions (restrict access, pause data flow, terminate) tied to severity.

5. Mistake: Evidence scattered across inboxes and shared drives.
   Fix: Use a single system of record per provider and a recurring evidence calendar. Daydream can hold the control mapping, tasks, and evidence set so audits become a structured export instead of manual collection.

Enforcement context and risk implications

No public enforcement cases were provided for this specific requirement in the supplied source set, so you should treat SA-9(3) primarily as an assessment and authorization readiness expectation under NIST SP 800-53. ²

Operational risk is straightforward:

• If trust conditions are unclear, providers will be onboarded with inconsistent controls.
• If trust is not maintained, you will miss material changes (subprocessors, hosting moves, degraded security posture) until after an incident.
• If evidence is thin, you may fail an assessment even if teams are “doing the work,” because you cannot prove it.

Practical 30/60/90-day execution plan

Days 0–30: Define the trust standard and minimum viable workflow

• Publish a Trust Relationship Standard with tiered requirements.
• Build the provider tiering decision matrix and intake checklist.
• Assign RACI and create a single repository structure for provider trust packages.
• Identify your top in-scope providers by criticality and access level.

Days 31–60: Retrofit critical providers and harden contracting

• Apply tiering to the critical provider list and document results.
• Gap-assess trust packages for those providers; open remediation items.
• Update contract templates / security exhibits to encode your trust conditions.
• Stand up event-driven reassessment triggers with Procurement and Security (who gets notified, where it is tracked, who approves).

Days 61–90: Operationalize “maintain” with monitoring and evidence cadence

• Implement recurring validation cycles per tier and schedule them.
• Run at least one tabletop reassessment for a realistic trigger (scope change or subprocessor notice) and retain evidence.
• Establish exception management with expiry dates and compensating controls.
• In Daydream, map SA-9(3) to the control owner, document the operating procedure, and attach the recurring evidence artifacts so your assessment packet is continuously current.

Frequently Asked Questions

Does SA-9(3) require a specific “trust framework” or formal trust model?

No specific model is mandated in the control text; you define the “requirements, properties, factors, or conditions” that constitute trust for your environment. What matters is that you document those conditions and maintain them over time. ¹

Can we satisfy SA-9(3) by collecting a SOC 2 report annually?

A report can support your trust decision, but SA-9(3) expects you to establish your own trust conditions and verify the provider meets them. If your conditions include contract terms, access constraints, or change notification, a report alone will not prove those are in place.

What counts as “maintaining” the trust relationship in practice?

Maintaining means recurring validation plus reassessment when material events occur. You should be able to show evidence of periodic reviews and at least one example of acting on a change trigger.

How do we handle SaaS providers that refuse audit rights or detailed security addenda?

Document the gap against your trust standard, apply compensating controls (scope restriction, reduced data sharing, stronger internal monitoring), and route the decision through formal risk acceptance with an expiry date. Keep the decision and rationale in the provider’s trust package.

Do fourth parties (subcontractors/subprocessors) fall under SA-9(3)?

If the external service provider uses subcontractors that affect your security boundary or data handling, your trust conditions should address them (disclosure, approval/notification, and flow-down requirements). Capture how you monitor those changes in your maintenance workflow.

What’s the minimum evidence an auditor will accept for SA-9(3)?

A documented trust standard, a completed provider-specific trust package showing the criteria applied, and records of ongoing validation or trigger-based reassessment. Auditors also look for proof that exceptions are tracked and resolved, not left as permanent open items.

Footnotes

1. NIST SP 800-53 Rev. 5 OSCAL JSON

2. NIST SP 800-53 Rev. 5