A TRIR OSHA calculation looks simple: multiply recordable incidents by 200,000, divide by hours worked. Two inputs. One formula. And yet, construction companies get it wrong constantly. A 2024 analysis of prequalification data across 1,200 specialty contractors found that 23% had errors in their self-reported TRIR -- some inflating their rate unnecessarily, others deflating it in ways that would not survive an OSHA audit.

Each mistake below distorts your incident rate and creates downstream problems in prequalification, insurance pricing, and regulatory compliance.

Mistake 1: Not Recording Incidents That Meet OSHA Criteria

This is the most consequential error and the most common. Under-recording produces an artificially low TRIR that misrepresents your safety performance.

The root cause is usually confusion about what constitutes "medical treatment beyond first aid." Field supervisors make recording decisions in real time, often without checking the OSHA first aid definition list. Common under-recorded scenarios:

Prescription medications. A worker sprains an ankle. The clinic doctor prescribes ibuprofen 800mg. Because ibuprofen is available over-the-counter, the supervisor assumes it is first aid. It is not. A prescription-strength medication (even if the active ingredient is available OTC) makes the case recordable.

Wound closures beyond butterfly strips. Steri-Strips qualify as first aid. Sutures, staples, and surgical glue do not. A supervisor who treats all wound closure methods the same will miss recordable cases.

Follow-up physical therapy. A single diagnostic visit to a physician is not medical treatment if no treatment is provided. But if the physician refers the worker to physical therapy and the worker attends a second appointment for treatment, the case becomes recordable.

Impact on TRIR: Each under-recorded incident reduces the numerator, producing a lower rate. For a 200-person sub working 400,000 hours, one missed incident changes TRIR from 1.50 to 1.00 -- a difference that might move them from conditional prequalification to automatic approval.

Mistake 2: Recording Non-Recordable Incidents

Over-recording is less common but equally distorting. It inflates TRIR and can disqualify a sub from projects they should access.

Frequent over-recording scenarios:

Tetanus shots. A worker gets cut by a rusty nail and receives a tetanus immunization. The supervisor records it as medical treatment. OSHA explicitly lists tetanus immunizations as first aid. Not recordable.

Diagnostic procedures. A worker reports back pain. The doctor orders an X-ray and sends the worker home with instructions to take OTC ibuprofen. No prescription, no restricted work, no days away. The X-ray alone is a diagnostic procedure, not treatment. Not recordable.

Observation visits. A worker bumps their head and the supervisor sends them to the ER for observation. The ER monitors the worker for 2 hours and releases them with no treatment. Observation alone is not medical treatment. Not recordable.

Impact on TRIR: Each over-recorded incident adds to the numerator. For a small sub working 100,000 hours, one extra recorded incident jumps TRIR from 2.00 to 4.00 -- potentially a disqualifying difference.

Mistake 3: Incorrect Hours Calculation

Hours worked is the denominator. Getting it wrong changes the rate proportionally, and the error direction depends on whether hours are over- or under-counted.

Common Hours Errors

Error	Direction	TRIR Effect	How It Happens
Including vacation/holiday hours	Inflates hours	Deflates TRIR	Using "paid hours" instead of "hours worked" from payroll
Excluding overtime hours	Deflates hours	Inflates TRIR	Only counting straight-time hours
Using headcount x 2,000 estimate	Either direction	Unpredictable	Lazy calculation instead of actual payroll data
Including office staff hours	Inflates hours	Deflates TRIR	Not separating field and office establishments
Double-counting multi-shift hours	Inflates hours	Deflates TRIR	Counting shift overlap hours twice

The fix is straightforward: use actual hours worked from payroll records. For construction companies, this means time-card hours including overtime, excluding PTO, sick leave, and holidays. Most payroll systems can produce this report directly.

Quantified impact: A 150-person contractor might report 312,000 hours (150 x 2,080 standard hours). But with overtime averaging 5 hours/week and 3 weeks of PTO per employee, actual hours worked might be 330,000. With 5 recordable incidents:

Estimated hours TRIR: (5 x 200,000) / 312,000 = 3.21
Actual hours TRIR: (5 x 200,000) / 330,000 = 3.03

A 6% difference. On a prequalification form, 3.21 vs. 3.03 could determine pass/fail against a 3.0 threshold.

Mistake 4: Mixing Employee and Subcontractor Hours

When a specialty contractor hires their own subcontractors (sub-tier subs), confusion arises about whose hours and incidents to include.

The rule: You only count YOUR employees' hours and incidents. If you subcontract drywall finishing to a smaller firm, their workers' hours do not go in your denominator and their incidents do not go in your numerator.

The exception: If you supervise temporary staffing agency workers on a day-to-day basis, their hours and incidents count as yours per OSHA's host employer guidance.

This mistake cuts both ways:

Including sub-tier hours without their incidents (deflates TRIR -- more hours, same incidents)
Including sub-tier incidents without their hours (inflates TRIR -- same hours, more incidents)
Including both (masks your actual rate with someone else's performance)

GCs who verify TRIR during prequalification should ask: "Does your reported hours figure include any subcontracted labor?" If yes, the calculation needs correction.

Mistake 5: Not Capturing First-Report Data Within 24 Hours

OSHA requires recording within 7 calendar days of learning about a recordable incident. But the recording decision depends on information gathered in the first 24 hours.

When a worker visits a clinic, the initial treatment determines recordability. But many construction companies do not have a system for getting the clinic report back to the safety manager the same day. The worker returns to the site, the supervisor assumes the treatment was minor, and the incident never gets evaluated for recordability.

Three weeks later, a workers' comp claim lands with the insurance carrier, revealing that the worker received stitches and a prescription. Now the safety manager must retroactively add a recordable case. If this happens near a prequalification deadline, the sub may have already submitted incorrect TRIR data.

Prevention: Establish a first-report protocol. Within 4 hours of a worker leaving the site for medical evaluation, the clinic should fax or email the treatment summary to the safety manager. Use a designated medical provider network where possible to ensure reporting compliance.

Mistake 6: Failing to Track 3-Year Rolling Average Correctly

The mathematical error here is averaging annual TRIRs instead of pooling all incidents and hours.

Wrong method:

2023 TRIR: 3.2
2024 TRIR: 1.0
2025 TRIR: 0.0
Average: (3.2 + 1.0 + 0.0) / 3 = 1.40

Correct method:

2023: 4 incidents, 250,000 hours
2024: 2 incidents, 400,000 hours
2025: 0 incidents, 350,000 hours
Pooled: 6 incidents, 1,000,000 hours
3-Year TRIR: (6 x 200,000) / 1,000,000 = 1.20

The wrong method gives 1.40. The correct method gives 1.20. The difference exists because the wrong method gives equal weight to a year with 250,000 hours and a year with 400,000 hours. The correct method weights each year proportionally.

This error penalizes growing companies (whose hours increase each year) and benefits shrinking companies.

Mistake 7: Using the Wrong Reporting Year for Multi-Year Cases

When a worker is injured in December and does not begin missing work until January, which year does the incident belong to? The answer affects TRIR for both years.

OSHA's rule: Record the incident in the year the injury or illness occurred, not the year the consequences began. If the injury happened December 15, 2025, the case goes on the 2025 log even if the first day away from work is January 3, 2026.

This creates a common mistake at year-end: safety managers who are rushing to finalize their annual 300A delay recording December incidents until January, inadvertently moving them to the following year's log.

For GCs verifying sub data, this means comparing OSHA 300 log entries against workers' comp first-report dates. If the dates do not align, ask the sub to explain the discrepancy.

Mistake 8: Ignoring Aggravation of Pre-Existing Conditions

A worker has chronic tendinitis from years of concrete finishing. During a pour on your project, the condition worsens significantly, requiring a cortisone injection. Is this recordable?

Yes. OSHA's recording criteria cover work-related aggravation of pre-existing conditions. If a workplace event or exposure significantly aggravates a pre-existing condition beyond what would have occurred from normal daily activities, the aggravation is recordable.

Construction supervisors frequently skip these cases, reasoning that the underlying condition was not caused by work. But OSHA does not require that work cause the condition -- only that work significantly aggravate it.

This mistake consistently under-reports musculoskeletal disorders in trades with repetitive motions: concrete finishing, drywall, masonry, and painting.

Mistake 9: Not Updating Records When Case Status Changes

An incident initially classified as first-aid-only may become recordable later. A worker gets a minor cut, receives bandaging (first aid), and returns to work. Three days later, the cut is infected and the worker receives a prescription antibiotic. The case is now recordable.

OSHA requires updating the 300 log when case status changes. Many companies record the initial classification and never revisit it. This creates systematic under-reporting of cases that started minor and escalated.

Similarly, a case initially classified as "other recordable" (medical treatment only) may later involve days away from work. The 300 log entry must be updated to reflect the more serious classification. This does not change the TRIR count (it was already recorded) but does affect the DART calculation.

Best practice: Review all open 300 log entries monthly. Check whether any first-aid cases have escalated and whether any "other recordable" cases have progressed to lost time or restricted duty.

Audit Checklist: Verify Your TRIR Accuracy

Verification Step	What to Check	Red Flag
Compare 300 log entries vs. workers' comp claims	Every comp claim should map to a 300 log entry	Comp claims without matching 300 log entries
Cross-reference hours with payroll	Hours on 300A should match payroll "hours worked"	Discrepancy greater than 5%
Review first aid classifications	Each first-aid case should cite specific OSHA first aid criteria	"First aid" cases involving prescriptions or sutures
Check recording dates	All entries within 7 days of incident	Entries added more than 30 days after incident
Verify 3-year calculation method	Pooled calculation, not averaged annual rates	Three separate TRIR values averaged together
Validate employee scope	Only company employees, not subcontracted labor	Hours that do not match headcount

FAQs

How do I know if my TRIR calculation is wrong? Compare your OSHA 300 log entries against your workers' compensation first-report-of-injury claims. Every comp claim should have a corresponding 300 log entry (though not every 300 log entry generates a comp claim). If you have comp claims without 300 log entries, you are under-recording. Also compare your reported hours against payroll records -- a discrepancy over 5% indicates an hours calculation error.

What happens if OSHA discovers recording errors during an inspection? OSHA can issue citations for recordkeeping violations under 29 CFR 1904. Willful failure to record is a per-instance violation with penalties up to $163,939 per violation (2026 penalty levels). Failure to maintain accurate 300 logs can also trigger a focused inspection of your safety program. Beyond penalties, corrected records will change your TRIR, potentially affecting active prequalification approvals.

Can a GC reject a subcontractor's self-reported TRIR? Yes. GCs can and should require OSHA 300 logs and 300A summaries as supporting documentation. Calculate the TRIR yourself from the raw data rather than accepting a number the sub provides. Many prequalification platforms perform this calculation automatically when the sub uploads their 300 logs.

How does hours inflation affect TRIR? Inflating hours worked reduces TRIR because the denominator increases while the numerator stays the same. For example, reporting 500,000 hours instead of actual 400,000 hours with 4 incidents changes TRIR from 2.0 to 1.6. This is a form of data falsification. GCs can detect it by comparing reported hours against headcount and project duration -- if the hours imply each worker averaged 60+ hours per week year-round, the number is likely inflated.

Should I record a case where the worker refused medical treatment? Recordability is based on treatment received, not treatment offered. If a worker suffers a laceration that would reasonably require stitches but refuses treatment and applies a bandage at home, the case is not recordable based on the first aid treatment actually received. However, if the injury involves lost consciousness, broken bones, or other conditions that are independently recordable regardless of treatment, refusing treatment does not exempt the case.

What if my TRIR changes after I have already submitted prequalification data? Notify the GC or prequalification platform immediately. Updated OSHA 300 logs with corrected data should be resubmitted. Most GCs re-run TRIR calculations quarterly. Submitting initially inaccurate data and correcting it proactively is far better than having a GC discover the discrepancy during an audit -- which can result in suspension from approved sub lists.

Catch TRIR Errors Before They Reach Prequalification

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