How to Write a Standard Operating Procedure

A standard operating procedure is only as good as the people who follow it. In regulated industries — medical devices, pharmaceuticals, aerospace, and others subject to FDA, ISO, or GMP oversight — an SOP that is unclear, incomplete, or inconsistently formatted isn’t just a documentation problem. It’s a compliance risk.

This guide walks through exactly how to write a standard operating procedure that works in practice: clear enough for a new employee to follow on day one, structured enough to satisfy an auditor, and specific enough that there’s no room for dangerous improvisation.

What Is a Standard Operating Procedure?

A standard operating procedure (SOP) is a written document that describes how to perform a specific task, consistently and correctly, every time. SOPs define the steps, the responsible roles, the required materials, and the expected outcomes for a given process.

In regulated industries, SOPs serve a second purpose: they provide an auditable record that your organization performs its processes in a controlled, documented way. When an FDA inspector or ISO auditor asks how your team handles a given procedure, your SOPs are the answer.

Well-written SOPs do three things:

Reduce variability — every operator follows the same steps in the same order
Accelerate training — new team members can follow a procedure before they’ve memorized it
Support compliance — documented processes satisfy regulatory and quality management requirements

Poorly written SOPs do the opposite. They create ambiguity, invite workarounds, and give auditors cause for concern.

The 7-Step Framework for Writing an SOP

Writing an SOP isn’t just about typing out a list of steps. It requires understanding the process, your audience, and the compliance context before you write a single sentence. Here’s a framework that works for regulated environments.

Step 1: Define the Purpose and Scope

Before anything else, be specific about what this SOP covers — and what it doesn’t.

The purpose is a single sentence describing why the SOP exists. Example:

“This SOP defines the process for receiving and inspecting incoming raw materials to ensure they meet quality specifications before use in manufacturing.”*

The scope defines the boundaries: which departments, products, equipment, or situations this procedure applies to. Scope statements prevent scope creep during revisions and prevent misapplication by operators who aren’t sure whether an SOP covers their situation.

If you can’t write a one-sentence purpose statement, the SOP is probably trying to cover too much. Break it into smaller, focused procedures instead.

Step 2: Identify the Audience

Who will follow this procedure? Who will approve it? Who might audit it?

Your primary audience is the operator — the person performing the task. Write at their technical level. An SOP for a lab technician can assume familiarity with basic lab equipment. An SOP for a field maintenance technician needs to be explicit about safety equipment and tool handling. An SOP designed for onboarding new hires needs to define every term.

Your secondary audience is the auditor. Every numbered step, every reference to a regulation, every approval signature is there partly to satisfy an external reviewer. Keep this in mind when deciding how much detail to include.

Step 3: Gather Subject Matter Expert Input

The worst SOPs are written entirely by technical writers who’ve never performed the procedure themselves. The best SOPs are co-authored by the people doing the work.

Interview the subject matter experts (SMEs) who own the process. Watch the procedure performed, if possible. Identify the steps that are tacit — things experienced operators do automatically but never verbalize. These are the gaps that cause new employee errors and audit findings.

Ask SMEs to review your draft and red-pen anything that doesn’t match how the process actually works. Regulatory agencies don’t just check that procedures are documented — they check that procedures are followed as written. If the SOP says one thing and your team does another, that’s a nonconformance.

Step 4: Draft the Procedure Steps

This is the core of the SOP. Each step should be:

Numbered — sequential steps, numbered sequentially, no exceptions
One action per step — if a step contains “and,” consider splitting it
Active voice, imperative mood — “Verify the temperature reads between 20°C and 25°C” not “The temperature should be verified”
Specific — include exact values, tolerances, time durations, equipment identifiers
Actionable — include decision points where the operator must branch (if X, proceed to step 7; if Y, stop and notify supervisor)

For complex procedures, group related steps under sub-headings. If your SOP requires equipment setup, sample preparation, execution, and cleanup, organize it that way. A reader scanning a 40-step procedure needs visual structure to keep their place.

Include references to related documents, forms, or equipment: “Complete form QC-007 and attach to the batch record.” Don’t reproduce the content of those documents inside the SOP — just reference them. This keeps your SOP focused and reduces the maintenance burden when those documents change.

Step 5: Add Compliance and Safety Callouts

Regulated SOPs need explicit callouts for regulatory requirements and safety risks. These are typically formatted as warning boxes, notes, or labeled paragraphs that are visually distinct from procedure steps.

Use a consistent vocabulary:

WARNING — a condition that could cause injury or equipment damage if ignored
CAUTION — a condition that could cause product nonconformance or data loss
NOTE — additional information that helps understanding but doesn’t require action

Regulatory cross-references belong in the SOP as well. If a step is required by FDA 21 CFR Part 820.70(a) (production and process controls), say so. If a step is required to maintain ISO 13485 compliance, note it. This gives auditors exactly what they need to trace your procedures back to regulatory requirements.

Step 6: Review, Approve, and Control the Document

An SOP that hasn’t been formally reviewed and approved is not an SOP — it’s a draft. In regulated industries, document control isn’t optional. Every SOP needs:

Author signature — who wrote it
SME review signature(s) — who validated that the procedure is technically accurate
Quality / regulatory approval — who authorized it for use
Effective date — when it became the controlled version
Revision number and history — what changed and when

Your document control system should ensure that only the current approved version is in use, and that superseded versions are archived but not accessible in the work area. Under FDA 21 CFR Part 820.40 and ISO 13485 section 4.2.4, inadequate document control is one of the most frequently cited nonconformances during inspections.

Step 7: Train and Maintain

A signed SOP means nothing if your team hasn’t been trained on it. Document training completion — either in a training record system or on the SOP itself — and capture the names and dates of employees who have demonstrated competency.

SOPs are living documents. Build a review schedule into your quality management system: most regulated organizations review their SOPs annually or whenever the underlying process changes. Track overdue reviews the same way you track overdue CAPAs.

When a procedure changes, issue a formal revision. Never hand-annotate a controlled SOP and continue using it. Every change should go through the full review-and-approval cycle.

SOP Template: Key Sections

Here’s the structure that satisfies most regulated industry requirements. Customize the section headers to match your quality management system’s document template.

1. Document Header

Document number (e.g., SOP-QC-0042)
Title
Version / revision number
Effective date
Department / owner
Author, reviewer, approver (with signature lines)

2. Purpose

One to three sentences stating why this SOP exists and what problem it solves.

3. Scope

What this SOP applies to (products, processes, locations, personnel). What it explicitly does not apply to.

4. Responsibilities

List the roles involved and their responsibilities. Use job titles, not names — procedures should outlast the people who wrote them.

5. Materials, Equipment, and References

Everything the operator needs before starting: equipment, reagents, forms, PPE. Cross- reference related SOPs, work instructions, and external standards.

6. Procedure

Numbered steps. Sub-headings for major phases. Decision trees for branching logic. Warnings, cautions, and notes formatted consistently.

7. Acceptance Criteria

How does the operator know the procedure was completed successfully? Define the expected outcome in measurable terms.

8. Abbreviations and Definitions

Define all acronyms and technical terms used in the document. Never assume the reader knows what GMP or QMS means — define it at first use and list it here.

9. Revision History

A table recording each revision: version number, date, description of changes, author. Auditors use this to understand the document’s history.

Compliance Callouts: FDA, ISO, and GMP

Understanding which regulatory frameworks apply to your SOPs changes how you write them.

FDA 21 CFR Part 820 (Quality System Regulation)

Part 820 governs quality systems for medical device manufacturers in the United States. It requires documented procedures for a broad range of activities including design controls (§820.30), document controls (§820.40), production and process controls (§820.70), and corrective and preventive actions (§820.100).

FDA inspectors will ask to see your SOPs and will observe whether your team follows them. Common findings include SOPs that haven’t been reviewed in over a year, procedures that describe a process your team no longer uses, and training records that don’t match the list of personnel who perform the procedure.

ISO 13485 (Medical Devices Quality Management)

ISO 13485 is the international standard for quality management systems in medical device manufacturing. Section 4.2 governs documentation requirements. ISO 13485 places particular emphasis on risk management integration — your SOPs should reference ISO 14971 risk analyses where applicable.

A key difference from FDA Part 820: ISO 13485 explicitly requires that your QMS be appropriate to the regulatory requirements of the country or countries where your devices are distributed. If you’re selling into the EU, that means MDR alignment.

GMP (Good Manufacturing Practice)

GMP requirements govern pharmaceutical manufacturing, food production, and other industries where product safety depends on process consistency. GMP SOPs typically require more explicit batch record references, environmental monitoring callouts, and cleaning validation steps than medical device SOPs.

Under FDA 21 CFR Parts 210 and 211 (pharmaceutical GMP), every critical process step must be documented in a procedure and verified against established limits. Deviations must be investigated and resolved through a CAPA process — your SOP should describe what constitutes a deviation and who to notify.

Common SOP Writing Mistakes

After reviewing hundreds of SOPs in regulated industries, the same mistakes appear repeatedly.

Steps That Aren’t Steps

“Ensure the equipment is calibrated” is not a step. A step is: “Verify calibration sticker on Instrument ID XYZ-01. If calibration date has expired, remove instrument from service and submit Work Order #WO-012 before proceeding.” Vague language is the most common reason procedures fail during execution and during audits.

Passive Voice

“The sample should be labeled” tells no one who is responsible or when to do it. “Label the sample container with batch number, date, and operator initials before proceeding to Step 12” leaves no ambiguity. Write in the imperative — give commands.

Overcrowded SOPs

Trying to document an entire process in a single SOP creates a document that’s too long to be useful and too broad to be auditable. If your SOP covers more than one distinct procedure, split it. A 5-page SOP for equipment cleaning and a 4-page SOP for equipment qualification are more useful than a 12-page SOP that awkwardly covers both.

Missing Decision Logic

Real processes have exceptions. What does the operator do when a measurement falls outside the acceptable range? If the SOP doesn’t tell them, they’ll improvise — and whatever they do won’t be documented. Map your decision points. Write the branches.

No Connection to Training Records

An SOP without a training record is an audit liability. Your document control system should link each SOP to the employees who have been trained on it. Auditors will ask.

How AI Accelerates SOP Writing for Regulated Teams

Writing SOPs in regulated environments is slow because the stakes are high. Every word matters. Terminology must be consistent. References must be accurate. Reviewers from multiple functions — engineering, quality, regulatory — all need to sign off before the document goes live.

AI writing assistance can reduce the time spent on the most mechanical parts of SOP writing: drafting initial step sequences, maintaining consistent terminology across a procedure library, and suggesting relevant regulatory cross-references based on your existing documents.

TechWrite’s context-aware autocomplete is built specifically for this workflow. Instead of drawing suggestions from generic internet content, it indexes your existing procedure library and surfaces relevant language from documents your team has already written and approved. When you’re drafting a cleaning verification step, it can suggest the phrasing your QA team uses in similar procedures — not a hallucinated approximation.

For teams managing hundreds of SOPs across multiple sites, consistency is the hardest problem. A term like “qualified operator” might appear in 40 different procedures, each with slightly different phrasing. TechWrite normalizes that by anchoring suggestions to your controlled document set.

If you’re evaluating documentation tools for your team, the technical documentation software comparison covers the key features to look for in a regulated environment. If you’re currently using Archbee and evaluating alternatives, our Archbee alternative page covers how TechWrite compares on the features that matter for compliance-heavy teams.

Start With One Procedure

The most common mistake regulated organizations make with SOP programs isn’t bad writing — it’s trying to document everything at once. Pick one process that causes the most recurring problems: training delays, inconsistent results, audit findings. Write that SOP first, get it through review and approval, and use it as the template for the next ten.

The structure, the review process, the document number scheme — these will clarify themselves after you’ve been through the cycle once. Don’t design the perfect SOP program before you’ve written your first SOP.