SOP (Standard Operating Procedure)

An SOP (standard operating procedure) is a written instruction that directs how a defined operation is performed. Its practical purpose is to make the expected method usable by the people assigned to perform the operation: what to do, in what sequence, and where to find supporting instructions or requirements.

These are practical distinctions, not a universal document hierarchy. Organisations may combine document types or use different names. An SOP can include detailed task instructions and a recording form; the directions and the completed evidence still serve different purposes.

For detailed approval, versioning, distribution and retirement mechanics, see document control. For task-level granularity, see the electronic work instruction reference. This article focuses on the procedure’s operational content, how people use it, and how its instructions connect to evidence of execution.

Start with the product and jurisdiction, not a generic list of SOP titles. The following map distinguishes US drug CGMP requirements from official guidance and practical document organisation. It is not a cross-sector mandatory SOP catalogue: a procedure library suitable for one manufacturing activity is not automatically suitable for another.

Binding US drug CGMP: coverage before titles

21 CFR 211.100(a) requires written production and process control procedures and connects their coverage to all requirements in that subpart. It does not supply a ready-made set of document titles. For the broader regulatory context, see 21 CFR 211.

As a practical document-design choice, a site can organise applicable requirements into linked procedures and supporting instructions. Test whether each requirement has an identifiable home and a usable instruction; counting SOPs or matching familiar titles does not establish coverage.

21 CFR 211.22(d) requires the quality control unit’s responsibilities and procedures to be in writing and those procedures to be followed. This adds an organisational dimension to the map: written procedures address quality-unit responsibilities as well as production activities.

Official guidance: broader documentation context

EudraLex Chapter 4 provides official guidance for interpreting medicinal-product GMP principles and guidelines. Check the current applicable framework for product scope and legal effect rather than assuming guidance has identical status in every jurisdiction.

Chapter 4, paragraph 4.29 addresses written policies, procedures, protocols, reports and associated records of actions or conclusions, where appropriate. Its breadth matters: treat the examples as documentation subjects, not a naming convention requiring one standalone SOP per subject.

Use ICH Q10 as the pharmaceutical quality-system reference alongside this procedure-level map. In practice, keep the source obligation, the site’s chosen document arrangement and the organisational context distinguishable. The broader cGMP reference provides a starting point for terminology.

An executable SOP lets a trained person identify what to do, when to proceed and what evidence to leave. The following is a practical design checklist, not a universally mandated template; headings and document layouts are site-defined.

• Purpose: the operational outcome the procedure supports.
• Scope and exclusions: where it applies and which activities it does not cover.
• Accountable roles: who performs, checks and makes decisions.
• Prerequisites: conditions that must be satisfied before starting.
• Equipment or materials: relevant identifiers, suitability checks and references.
• Ordered actions: the sequence, including branches and handoffs.
• Acceptance or decision criteria: how to distinguish an acceptable result from one needing assessment.
• Required records: what to capture and where to record it.
• Stop and escalation conditions: when to pause and whom to contact.
• Related instructions: supporting methods or task-level directions.
• Revision rationale: what changed and why.

Keep product-specific manufacturing instructions in the master batch record, with appropriate cross-references. Use good documentation practice for recording conventions rather than restating those conventions in every step.

Instruction versus execution evidence

Instruction: “Before use, check the equipment identifier against the assigned equipment.” Execution evidence: the associated record identifies the equipment-use event, check result, performer and SOP revision used. That evidence can sit in a separate form or electronic transaction; it need not be written on the SOP itself.

Relationships that preserve context

An illustrative data model starts with a procedure and its revisions. Each revision carries approval identity and effective status. Training assignments and controlled copies identify a revision; the resulting training record retains that context. Execution records preserve the revision used within the batch execution history, while exceptions link to affected execution. These relationships support traceability without prescribing a database or application: the same logic can be implemented through controlled paper references or electronic links.

For US drug production and process control procedures, 21 CFR 211.100(a) requires drafting, review and approval—including changes—by the appropriate organisational units, plus review and approval by the quality control unit. Under 21 CFR 211.22(c), the quality control unit is responsible for approving or rejecting procedures and specifications affecting the drug product’s identity, strength, quality and purity.

As guidance, ICH Q10, section 5, Change Management defines change management as a systematic approach connecting proposal, evaluation, approval, implementation and review. Use change control to organise the impact assessment rather than treating an SOP revision as an isolated editing task.

Approval of the instruction and readiness to use it are separate operational decisions. The following seven-step workflow is a site-designed sequence, not a prescribed regulatory status model. Assign a procedure owner to coordinate it, with authorised people making approval and activation decisions.

1. Propose and assess: the owner identifies the reason for change, affected operations, dependencies and intended scope.
2. Draft: process specialists translate the intended method into instructions that reflect the actual equipment and operating context.
3. Review: affected functions test technical accuracy, usability and consistency with linked instructions and forms.
4. Approve: obtain the applicable organisational and quality approvals before treating the text as an approved instruction.
5. Check readiness: responsible managers confirm affected roles, training readiness, linked forms, equipment context, point-of-use availability and arrangements for work already in progress.
6. Activate: an authorised person confirms the agreed transition conditions and communicates when and where the revision applies.
7. Review and retire: the owner checks whether the procedure works as intended, initiates needed changes and coordinates withdrawal when it is superseded or no longer needed.

Keep detailed version numbering, approval routing and archival mechanics within document control. The lifecycle question here is whether ownership and operational readiness are clear at each handoff.

For US drug-product operations, 21 CFR 211.25(a) requires CGMP training—including the regulations and written procedures required by them—as those requirements relate to the employee’s functions. The same paragraph requires CGMP training by qualified individuals, on a continuing basis and frequently enough to maintain familiarity with applicable requirements. This is not a prescribed annual training interval.

For each SOP revision, make a local training-impact decision: identify affected roles, specify which actions have changed, and select a learning or assessment method proportionate to the task. Use a training matrix to connect people and roles to the revision they need. Record the revision, method and outcome so that readiness is traceable to the changed work, not merely to the SOP title.

Document acknowledgement records that someone has acknowledged the instruction; it does not, by itself, demonstrate task ability. Choose competency assessment methods according to the changed action and its consequences. A practical demonstration may suit a changed hands-on task, but it need not be imposed for every editorial correction. Document the rationale for the chosen response.

A system hard-block preventing task access until specified training conditions are met is an optional implementation control, not a universal requirement of this paragraph. Define its scope by task, role and revision, together with exception handling, escalation and authorised decision-makers. An exception path should not silently turn an incomplete assessment into a completed one.

Worked case: completion is not shift coverage

Assume six assigned operators require practical demonstration under site policy. Four have passed; two have not yet been assessed. Completion is 4 ÷ 6 × 100 = 66.7%, rounded to one decimal place. That percentage does not establish coverage for a shift needing particular roles: the four assessed operators may not cover every required assignment. Nor does it authorise either unassessed operator. Check named people against the shift’s tasks and local authorisation criteria.

For medicinal-product GMP, EU guidance in Chapter 4, paragraph 4.1 calls for stated relationships and controls covering master documents, official copies, data handling and records in both hybrid and homogeneous systems. In a hybrid record system, controlling the electronic master alone does not address every place an instruction can remain usable.

Chapter 4, paragraph 4.2 also says reproduction of working documents from masters should not introduce errors. Practical checks therefore address both revision identity and reproduction accuracy: missing pages, clipped tables or unreadable symbols can undermine an otherwise current copy.

• Check printed binders, local downloads, shared folders and cached workstation views—not just the central library.
• At the point of use, compare the procedure identifier and revision with the effective source; confirm that the displayed or printed instruction is complete and readable.
• Keep withdrawal evidence identifying the location, superseded revision, action taken, responsible person and date. Confirm that shortcuts and cached views no longer lead operators to an obsolete execution copy.

These are practical distribution controls, not a prescribed checklist. A superseded copy retained for historical reference serves a different purpose from one available for routine execution. Clearly distinguish those uses and preserve the historical instruction associated with completed work under records retention arrangements. Use document control for withdrawal and archival mechanics; removing obsolete instructions from routine use should not erase the history of how work was performed.

EU GMP guidance in Chapter 4, paragraph 4.4 says document language should fit its intended use and SOPs, work instructions and methods should use an imperative mandatory style. Write instructions as actions, not descriptions of what usually happens.

• Use one action per step where practical. Name the actor whenever responsibility changes.
• Put prerequisites before dependent actions, and warnings or stopping rules before the affected operation.
• State observable acceptance criteria: what to inspect, where to read the result and what permits progression.
• Replace “suitably,” “normally” and “as necessary” with a decision rule or a named authority responsible for deciding.

Worked case 2: replace “mix thoroughly”

Assume an illustrative site-approved process specifies 100 rpm for 10 minutes, timed only after reaching the setpoint, and has a defined interruption procedure. Here, rpm means revolutions per minute; duration is measured in minutes. These values are illustrative, not transferable processing settings.

1. Operator: if mixing is interrupted, follow the site-approved interruption procedure before restarting or deciding how much mixing time remains.
2. Set the mixer speed to 100 rpm.
3. Observe the speed display. Start the timer only when the display reaches 100 rpm.
4. Mix at 100 rpm for 10 minutes from that timing start.
5. Check and record the elapsed mixing time and observed speed before proceeding.

Test the draft through a point-of-use gemba walkthrough with a representative user. This human-factors check should expose inferred prerequisites, searches for missing criteria and unwritten workarounds. Where line clearance supports cross-contamination control, check that the user can identify what must be removed before starting.

For US drug CGMP, 21 CFR 211.100(b) requires written production and process control procedures to be followed during execution and documented at the time of performance. This connects the instruction to contemporaneous recording, not merely to a completed signature field.

The same provision separately requires any deviation from written procedures to be recorded and justified. Keep that obligation distinct from the site's additional investigation, escalation and approval workflow.

A practical recovery sequence

The following is an operational approach, not the literal sequence prescribed by the regulation. Adapt containment and decision authority to the activity and its risks.

1. Establish the known execution state: the last evidenced step, work in progress, and any uncertainty about what occurred.
2. Contain the affected activity as appropriate: pause work, identify affected material or equipment, and preserve relevant records.
3. Identify the SOP, revision and specific instruction involved so the departure can be assessed against the applicable direction.
4. Record the departure, timing and relevant observations. Link supporting readings or a process event log; distinguish observations from assumptions.
5. Route impact assessment to the site's designated authority, identifying what remains uncertain and what decision is needed.
6. Document the decision and conditions for continuation, including permitted actions, checks, limits and circumstances requiring another decision.

A late signature does not replace missing execution evidence. Preserve the gap explicitly rather than treating retrospective sign-off as proof that the step occurred.

Keep the decision bounded

For temporary departures, name the designated decision authority in the site's workflow rather than assuming a universal approving job title. Define the affected execution, permitted departure, duration or endpoint, and return-to-normal conditions.

Keep three events separate: a deviation concerns an exception during execution; change control addresses a proposed future instruction; corrective action within CAPA addresses a cause. A recorded deviation does not itself revise the standing SOP. Where these processes connect, cross-reference their records without treating one decision as a substitute for the others.

An illustrative integration connects procedure management, training records and MES through four steps. These are product-neutral design choices, not functions attributed to a named product or universal GMP requirements:

1. Resolve the applicable SOP revision for the operation, using its product, process and execution context.
2. Evaluate the assigned person's relevant role readiness against that revision and route unresolved readiness to an authorised person.
3. Present the instruction with its identity and revision visible at the point of execution.
4. Associate execution evidence with that revision, operation and person so the electronic batch record preserves a traceable batch execution history.

“Show the latest document” is insufficient for every open execution: a revision may change while work is underway. Building on the lifecycle discussion above, define an explicit transition decision for work in progress—continue under the applicable revision, pause, or transition with authorised instructions. Retain the historical revision context rather than replacing the document reference on completed events.

Worked case 3: reconcile an interrupted interface

Assume an interface submitted 17 execution acknowledgements and received confirmation for 15. The difference is 17 − 15 = 2 unconfirmed acknowledgements, not necessarily two unperformed actions. Reconcile each by event identifier. Check the receiving system before retrying; retry only unresolved transmissions using duplicate-prevention controls. Preserve the reconciliation decision and its basis in the event history for audit trail review. Do not repeat a physical operation merely because its acknowledgement is missing.

For data integrity, retain trustworthy links between instructions, actions and records through consistent production context tagging. Keep activation, exception approval and product disposition with authorised people. A software status supports those decisions; it does not replace their authority or judgement.

Use these qualitative checks to find contradictions between documents, actual work and management assumptions—not to rank inspection findings. Obsolete copies, role readiness and interrupted interfaces are covered above; here, test whether the instructions agree with each other and with the task.

During a gemba observation or internal audit, ask an operator to trace one task through its SOP and associated form. Compare what management expects with what the operator can actually do, record and escalate. For a revised instruction, use an effectiveness check to examine changed behaviour rather than treating publication as resolution.

Review signals include recurring clarification requests, repeated use of the same workaround, contradictory entries on linked forms and exceptions clustering around one instruction step. Treat these as prompts for assessment, not proof that rewriting the SOP is the right action. Root cause analysis may point instead to equipment constraints, form design, training or an impractical process sequence. Compare those explanations with observed work before selecting an action.

For medicinal-product GMP, EU guidance in Chapter 4, paragraph 4.5 says Quality Management System documents should be regularly reviewed and kept up-to-date. Treat the review as a test of operational fitness, not merely confirmation that the document has an approval signature.

As a practical implementation check, use a representative user and a sampled execution to test the following:

• Can the user identify the applicable instruction for this task, equipment and location?
• Can the next action be determined without guessing, including when to stop?
• Are referenced forms consistent with the steps, terminology and required entries?
• Can a reviewer reconstruct the revision used for a sampled execution, such as one documented in a batch record?
• Is the person authorised to decide on an exception clearly identified?
• Does the instruction still match the equipment, process and operating environment?

For review planning, combine a site-selected periodic interval with event-driven reassessment after relevant process changes, recurring exceptions or usability findings. Use quality risk management to prioritise procedures where ambiguity or outdated instructions could have the greatest impact. This practice recommendation does not impose a universal annual deadline.

Record what was checked, the outcome and its rationale—including a justified decision that no revision is needed. For failed tests, assign an owner and follow-up action rather than closing the review as complete. Keep approval, distribution and retirement mechanics within document control; the review should establish whether the instruction remains fit for use.