AQL (Acceptance Quality Limit)

AQL – Acceptance Quality Limit

This topic is part of the SG Systems Global regulatory glossary series.

Updated October 2025 • QC Sampling • QMS / WMS / MES

Acceptance Quality Limit (AQL) defines the worst tolerable process average of nonconforming units for a sampling plan. In practice, AQL drives how many units to inspect and the accept/reject cutoffs for incoming materials, in-process checks, and finished goods—so release decisions are consistent, defendable, and fast.

“No AQL = arguments and delays. Clear AQL = predictable release, clean evidence, and supplier accountability.”

1) What It Is

AQL is not a pass rate; it’s a risk parameter used with standard sampling schemes to set sample size and decision thresholds. You choose an AQL (e.g., 1.0% for majors), an inspection level (e.g., General II), and a lot size. The scheme returns a sample size (n) and accept/reject criteria (Ac/Re). You then execute inspection, classify defects, and disposition the lot.

TL;DR: Pick AQL + inspection level → get sample size & Ac/Re → inspect → disposition → trend. Tighten or relax based on risk.

Where it applies. Receiving (raw materials, APIs/excipients, packaging), in-process controls (weights, torque, pH, fill), and finished goods audits. Outputs feed CoA, supplier scorecards, and APR/PQR.

Defect classes. Most programs use three categories: Critical (safety/identity/labeling that could cause harm; typically 0% tolerance), Major (function/identity issues affecting use), and Minor (cosmetic or low-risk). AQL values are usually tightest for criticals, looser for minors.

2) Practical Implementation & Governance

Ownership. QA defines AQL tables by material type & risk; QC executes; Supply Chain ensures suppliers are contractually aligned; QA approves changes and monitors trends.

Inputs you’ll actually need:

  • Material master rules (required tests, AQL per defect class, inspection level, tightened/normal/reduced state).
  • Inspection methods with sampling instructions, measurement tools, and defect codes in QMS/LIMS.
  • Lot status workflow (Quarantine → Released/Rejected/Blocked) in WMS, enforced by barcode.
  • Exception routing to Deviation/CAPA/Change and supplier actions.

Risk-based tuning. You can tighten AQL after failures or critical events, and reduce AQL/inspection frequency after a strong acceptance run. Keep the logic in a controlled SOP and record state changes (tightened/normal/reduced) with reasons.

Common pitfalls. Treating AQL as a guaranteed defect rate; mixing sampling levels ad-hoc; missing traceability from item master → sample list → defect classification; failure to update AQL after repeated supplier issues; no link to batch genealogy and CoA.

3) Example (Conceptual) & Decision Logic

Scenario. Lot size 12,000 labels, AQL for Majors = 1.0%, inspection level = General II. The scheme yields a sample size (n) and decision limits (Ac/Re). Suppose Ac=2, Re=3 for Major defects. If inspection finds 2 or fewer Majors → Accept; 3 or more → Reject; any Critical defect triggers automatic rejection regardless of Ac/Re for Majors/Minors.

Decision log (what auditors read):

  • Material & PO → rule set applied (AQL 1.0% Major, General II, state=Normal).
  • System-generated sample size & labels (traceable list of units).
  • Defects recorded by code/class (Major, Minor, Critical).
  • Computed decision vs. Ac/Re; approver e-sign and timestamp.
  • Lot status change (Quarantine → Released/Rejected) with reason and link to CoA or Deviation/CAPA.

4) Metrics, Trending & Supplier Scorecards

  • First-pass acceptance rate by supplier/material (rolling 3/6/12 months).
  • Defect Pareto (critical/major/minor) and top defect codes.
  • Cycle time (receipt → disposition), including hold aging and re-inspection frequency.
  • State changes (tightened/normal/reduced) with triggers and effectiveness checks.
  • APR/PQR contributions (trend charts, supplier re-qualification decisions, CAPA closure velocity).

5) How It Relates to V5

V5 by SG Systems Global operationalises AQL end-to-end so sampling isn’t a spreadsheet gamble—it’s a controlled, auditable process.

  • WMS gating. Auto-Quarantine at receipt; barcode enforces location and prevents release until inspection passes; allergen/quarantine zoning respected during picks.
  • QMS inspections. Methods embed AQL rules and defect codes; system computes sample size and Ac/Re; failures auto-raise Deviation/CAPA; supplier actions tracked.
  • MES prompts. In-process sampling steps with e-sign and reason codes; results map to batch/lot genealogy; exceptions block downstream steps.
  • Audit trail & Part 11. Every disposition, override, and signature is attributable and time-stamped—see Audit Trail (GxP) and 21 CFR Part 11.
  • Reporting. Supplier scorecards, defect Pareto, acceptance trendlines; CSV/XML exports for deeper statistical analysis.

Example flow. Receive lot → WMS sets Quarantine → QMS calculates sample size & Ac/Re → execute inspection & classify defects → pass = auto-Release; fail = Deviation + supplier CAPA; all results flow to CoA and APR/PQR dashboards.

6) Implementation Playbook (Team-Ready)

  • Define rules. Set AQL per material risk and defect class; choose inspection levels; specify triggers for tightened/normal/reduced states.
  • Configure systems. Load rules into item masters; configure QMS/LIMS methods; enable WMS status transitions and barcode checks.
  • Train & enforce. Receiving/QC use scanner-driven sample lists; e-sign all dispositions; no manual workarounds.
  • Trend monthly. Monitor first-pass acceptance, defect Pareto, chronic suppliers; escalate per SOP.
  • Close the loop. CAPA for recurring defects; verify effectiveness; update AQL or specifications as evidence dictates.

Related Reading

7) FAQ

Q1. Does AQL tell me the defect rate of the lot?
No. AQL sets sampling risk. It supports a decision with known risks; it doesn’t measure every unit.

Q2. When should I tighten AQL?
After failures, critical defects, or supplier drift. Define objective triggers in your SOP and record state changes.

Q3. How do AQL rules appear on the CoA?
CoA lists the tests and results; AQL logic sits behind the inspection plan. Keep the decision log and sample records available for audit.

Q4. Can I mix AQL levels for one lot?
Only if specified in your approved plan (e.g., Critical at 0.065%, Major at 1.0%, Minor at 2.5%). Random mixing undermines control and will draw findings.

Related Glossary Links:
• Data Integrity & Systems: Part 11 | Audit Trail
• Quality Ops: CoA | APR/PQR
• Execution Systems: MES | WMS | QMS



Related Business Terms and Concepts