Practical review
What to check in this situation
- Confirm liability and every injury to be assessed before arranging the assessment.
- Use a trained assessor and the NSW guideline edition in force at assessment.
- Understand the post-1 July 2026 principal-assessment effect across several entitlements.
Records that may help
Keep accepted-injury documents, complete treatment records, imaging, operative reports, prior impairment material and assessor instructions.
Next procedural step
Independent legal advice is required before a post-1 July 2026 assessment for ordinary workers; do not treat an online estimate as an assessment.
What WPI does and does not decide
WPI measures permanent medical impairment. It can be used for Section 66 compensation and, through the principal-assessment framework, other statutory thresholds. It does not by itself decide whether the worker can perform a particular job, whether treatment is reasonably necessary, whether the employer was negligent or what a claim is worth.
The NSW workers compensation claim guide explains how those separate entitlements and disputes fit together.
How a NSW permanent impairment percentage is built
For a WPI report review, a valid WPI opinion should show a chain from the accepted diagnosis to the applicable NSW method, measured findings, any regional conversion, any permitted combination and any pre-existing impairment deduction. This matters when tracing the assessor's percentage from diagnosis through measurement, conversion, combination and deduction; a report that only records an examination does not explain the percentage.
1. Confirm the body system and diagnosis
Spine, upper limb, lower limb, hearing, respiratory, skin, neurological and primary psychiatric impairments use different methods. The referral should identify the accepted injury and any consequential physical condition being assessed.
2. Decide whether maximum medical improvement has been reached
In a WPI report review, NSW Guidelines paragraph 1.15 requires a well-stabilised condition unlikely to change substantially in the next year, with or without treatment. If adequate treatment could still materially improve the assessed condition, paragraph 1.16 requires the timing to be deferred.
3. Apply the correct NSW/AMA method and measure the required findings
When preparing a WPI report review, the NSW Guidelines prevail over AMA5. The body system determines whether the assessor measures DRE clinical features, active joint movement, nerve sensory and motor loss, audiometric thresholds, pulmonary function, skin criteria, neurological function or the six PIRS domains.
4. Convert regional values and combine only where permitted
For a WPI report review, a digit, hand, upper-extremity, foot or lower-extremity value may require conversion before it becomes WPI. Permitted physical WPI values use the AMA5 Combined Values Chart rather than ordinary addition. For example, 20% WPI combined with 10% WPI is 28%, because the second value applies to the remaining 80%. This arithmetic only demonstrates the chart.
5. Explain deductions and excluded methods
In a WPI report review, a pre-existing diagnosis does not justify an automatic deduction. Section 323 first requires a finding that a previous injury, pre-existing condition or abnormality actually contributed to the assessed degree of permanent impairment. Only the proportion due to that earlier impairment is deducted. AMA5 Chapter 18 pain is excluded; pain is ordinarily addressed through the underlying diagnosed condition. Primary psychiatric WPI is assessed separately and cannot be combined with physical WPI, secondary psychiatric impairment is not assessed for WPI, and NSW excludes using ADL to alter upper- or lower-extremity ratings.
Worked illustration: a pre-existing impairment deduction
In this illustration of a WPI report review, assume the body-system method produces 20% WPI and the assessor first finds that an earlier condition contributed to that assessed impairment. If the extent of that contribution is too difficult or costly to determine, section 323 permits an assumed deduction of one tenth of the impairment unless that assumption is at odds with the available evidence. One tenth of 20 is 2, so the arithmetic produces 18% WPI after deduction.
The threshold finding matters. In Walton v State of New South Wales (Hunter New England Local Health District) [2026] NSWSC 824, the Court explained that the mere existence of a condition, or evidence that it caused pain, is not enough. The condition must have increased or contributed to the degree of impairment being assessed before the one-tenth assumption can be used. The figures above explain deduction arithmetic only and do not predict an individual result.
Read the Walton section 323 case note or section 323 in the current 1998 Act.
Sources for this framework
Sources used for a WPI report review: NSW Workers Compensation Guidelines for the Evaluation of Permanent Impairment, Fourth Edition, paragraphs 1.6-1.24 and 1.27-1.31; AMA5 Chapters 1-2 and the Combined Values Chart at pages 604-606. NSW uses AMA4 Chapter 8 for the visual system. The body-system guides identify the additional paragraph and table where relevant.
Choose the body-system permanent impairment guide for the measurements, conversion steps and verified examples relevant to the injury.
The body system determines the method
The NSW Guidelines prevail over the adopted medical guides. Spine assessment generally uses NSW-modified DRE categories. Upper and lower limbs may involve measured movement, diagnosis-based methods, joint replacement scores or nerve deficits. Hearing uses the NSW hearing methodology. Vision uses AMA4 Chapter 8. Primary psychiatric impairment uses PIRS and remains separate from physical WPI.
AMA5 Chapter 18 pain is excluded in NSW workers compensation. Pain is usually considered within the method for the underlying diagnosed condition. A symptom, scan finding or operation does not create a fixed percentage without the required clinical criteria.
Choose the body-system assessment guide for the measurements and source references relevant to the injury.
Current process
Permanent impairment assessments from 1 July 2026 to mid-2027
NSW is in an interim period. Separate examinations arranged by the worker and insurer can still occur, but an interim assessment must be performed by an assessor on SIRA's register. Liability for the injury must have been determined before an interim assessment is made.
Independent legal advice is compulsory
A worker must receive independent legal advice about the full legal implications before being seen by a permanent impairment assessor. Advice is also required before entering an impairment agreement.
The assessment can affect several entitlements
The principal assessment is used across weekly payments, medical and related treatment expenses, Section 66 lump sum compensation, commutation access and work injury damages. It is not only a lump sum calculation.
Agreement or medical dispute
If the worker and insurer agree on the degree of impairment, they may enter a written impairment agreement. If they do not agree, the insurer must give written notice and either party may refer the disagreement to the Personal Injury Commission as a medical dispute, supported by medical evidence.
A further assessment is tightly restricted
A second or later assessment during the interim period requires agreement that there appears to be unexpected and material deterioration. The deterioration must be capable of increasing the impairment by at least a further 10 percentage points. Ordinary age-related deterioration does not meet that test.
Important transitional rules
If a pre-reform assessment made before 1 July 2026 has not yet been used for a Section 66 claim, SIRA says the claim must be made before 1 July 2028. No new Section 66A complying agreements can be entered from 1 July 2026. A different permanent impairment process is expected to commence from mid-2027.
The 2026 principal-assessment changes do not apply in the same way to exempt workers (police officers, paramedics and firefighters), coal miners, volunteers, dust disease claims or claims with a pre-2002 injury date.
Last reviewed 20 July 2026. Sources: SIRA worker guidance and SIRA interim assessment guidance. See also the PIC dispute guide.
Evidence to prepare before assessment
- the accepted injury description, injury date and any consequential physical conditions;
- treating GP and specialist records, imaging, operative reports and rehabilitation material;
- records showing whether maximum medical improvement has been reached;
- earlier injury and pre-existing-condition records relevant to any section 323 issue;
- the worker's treatment history, current symptoms and functional account;
- all reports relied on by the worker or insurer, including earlier impairment assessments.
How to read the report
- Confirm that every accepted injury intended for assessment is identified.
- Check that the assessor explains maximum medical improvement.
- Find the NSW paragraph and adopted table or category used for each body system.
- Trace any regional conversion and use of the Combined Values Chart.
- Check that physical and primary psychiatric impairment have not been combined.
- For any section 323 deduction, identify the evidence that the earlier condition increased the assessed impairment and how the proportion was chosen.
The Walton case note explains why a pre-existing diagnosis or pain history is not enough by itself to trigger a deduction.
If the assessment affects another decision
A weekly-payment or treatment decision must be assessed under its own statutory rules. If an insurer relies on a WPI result to stop or reduce another entitlement, keep the impairment report and the decision notice separate and check the reasons and review pathway for each.
Common questions
What does WPI mean?
WPI means whole person impairment. It is a medical percentage assessed under the NSW Workers Compensation Guidelines. It is different from a diagnosis, work capacity opinion or compensation amount.
When can permanent impairment be assessed?
The condition must generally have reached maximum medical improvement: it should be well stabilised and unlikely to change substantially in the next year, with or without treatment. Assessment may need to be deferred if treatment could materially alter the impairment.
Does every assessment use AMA5?
No. The NSW Guidelines control. They adopt and modify AMA5 for many body systems, use AMA4 Chapter 8 for vision, the NSW hearing method for hearing loss and PIRS for primary psychiatric impairment.
What if the worker and insurer disagree about the percentage?
During the current interim process, the insurer must give written notice if an impairment agreement is not reached. Either party may then refer the disagreement to the Personal Injury Commission as a medical dispute and must support its position with medical evidence.
Does a pre-existing condition always reduce WPI?
No. Section 323 requires the earlier injury, condition or abnormality to have contributed to the assessed degree of impairment. Only that contribution is deducted. The one-tenth assumption is used only where the proportion is too difficult or costly to determine and is not inconsistent with the evidence.
Need help reading a WPI report?
Call (02) 7233 3661 with the report and insurer correspondence available, or use the claim-check form below.
Last reviewed 20 July 2026. This information is general in nature and is not legal or medical advice. Obtain advice about the assessment and its effect on your own entitlements.