What it means
An operator may find that a machine ran outside its set range, a supplier used an alternate material or a required test was missed, and a verbal explanation can be forgotten across shifts. A log captures what happened, when, which batches or customers might be affected and what immediate containment took place.
Describe the approved requirement and the observed difference, because a note saying only that the temperature was wrong is not enough; record the specified range, actual reading, duration, instrument and product identity where relevant. Attach source evidence and note who entered the record, then give each deviation a stable ID linked to affected lots, equipment and the governing specification version.
If a later investigation expands the scope, add the new lots without overwriting what was first known, because that history helps an auditor reconstruct the decision. If the event involves safety or regulated products, follow the applicable escalation and reporting rules, not merely the ordinary log workflow.
Separate containment from final decision: a team may stop the line and quarantine goods immediately, and investigation then determines cause, scope and risk. An authorised reviewer may approve rework, reject goods or allow a documented concession where permitted.
A log entry should show the decision and evidence, not assume all deviations can be waived. Link recurring issues, since five small deviations from the same machine can be more important than one isolated large one.
Categorise by cause, equipment, supplier or step, but avoid turning the categories into a way to hide events. Corrective action should address why the deviation happened and how recurrence will be checked.
Keep the original record when details are corrected, so an audit trail shows what was known at the time and what changed after investigation. Classify the current status separately from the final outcome, because reported, contained, under review, dispositioned and effectiveness pending are not the same state.
The team should see open risks even if paperwork for one stage is complete. Backdating a result or deleting a deviation to keep a clean report damages trust and may hide affected product.
For managers, the log is a learning tool that helps determine whether controls catch problems in time and whether actions really reduce repeat events, while preserving a clear decision trail for each affected batch.
In practice
Real-world examples.
Example
A food line records a four-minute temperature excursion, quarantines the batch and waits for a quality decision.
Example
A supplier sends a part with a different coating from the approved drawing. Procurement logs it and asks engineering for a disposition before use.
Example
A monthly review finds repeated calibration-related deviations on one machine and opens a corrective action rather than treating each as unrelated.
Formula
Calculation
Deviation recurrence rate = Repeated deviations of defined type / Total deviations of that type during period x 100
Worked example. A fictional factory records 20 deviations during a quarter. Six repeat a previously identified seal-setting issue.
- Recurrence share = 6 / 20 x 100 = 30% of logged deviations.
- The team should also review production volume and reporting completeness before claiming the process is improving or worsening.
The log's primary purpose is traceability and disposition, not hitting a numerical target.Case study
Seen in the real world.
This illustrative and entirely fictional example follows Meadow Packaging, an invented packaging plant. An operator noticed that a sealing machine briefly ran below its approved temperature. The supervisor adjusted the setting and wanted to continue, assuming the affected cartons looked fine. The operator recorded the deviation with time, machine, readings and affected batch numbers.
Quality held the identified cartons, tested a sample under its procedure and decided which could be reworked. A review showed a sensor connection had been failing intermittently and maintenance fixed it. Meadow kept the log open until the disposition and preventive check were recorded. The event cost time, but the business avoided sending goods whose seals had not been properly assessed.
At the next shift, another operator finds a similar temperature dip. The linked log entries show a pattern that a single repaired carton would not reveal. Quality checks whether the earlier sensor fix actually worked and widens the affected period if the new evidence requires it.
Watch out
Common mistakes.
- Writing a vague note without the approved standard, actual observation, time and affected items.
- Treating immediate adjustment as proof that already-produced goods are safe or conforming.
- Deleting or backdating a record after the final result looks acceptable.
Questions
People also ask.
Is every deviation a defective product?
No. Investigation determines the effect. A process departure can be harmless, require rework or make goods unusable.
Who can close a deviation?
Follow the business's quality authority and applicable rules. The person who observed it may not have authority to approve affected goods.
Is a deviation log the same as corrective action?
No. The log records the event and disposition; corrective action addresses cause and recurrence where needed.
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