How to Fill Out Michigan WDCA Form WC-105 + FAQs

Michigan WDCA Form WC-105, the Notice of Dispute, is the document an employer or its workers’ compensation insurance carrier files with the Michigan Workers’ Disability Compensation Agency to formally reject all or part of a claim for benefits under the Workers’ Disability Compensation Act. The form tells the agency, the injured worker, and the worker’s attorney that benefits will not be paid voluntarily and that the dispute is now part of the official record.

Filing the form late, leaving fields blank, or writing a vague reason for the dispute can trigger statutory penalties under MCL 418.801, interest on unpaid benefits, and an order from a magistrate forcing payment. The current revision of the form is dated Authority: P.A. 317 of 1969, as amended and is hosted on the WDCA’s official forms library. According to WDCA annual data, Michigan employers and carriers file roughly 18,000 to 22,000 dispute and benefit notices each year, and a meaningful share are rejected on first review for missing fields or unclear dispute language.

Here is what you will learn in this guide:

• 📝 How to complete every box on Form WC-105 the way a magistrate expects to see it
• ⏱️ The 14-day clock that controls when the form must reach the agency
• 📂 Which documents to gather before you open the form so nothing slows you down
• 💼 Three real filer scenarios walked through line by line
• ⚖️ The penalties, interest, and case-law consequences of getting it wrong

What the Form Is and Who Must File It

Form WC-105 is the Notice of Dispute used under the Michigan Workers’ Disability Compensation Act, Public Act 317 of 1969. The form notifies the WDCA, the injured employee, and the employee’s representative that the employer or its insurer disputes liability for some or all of the workers’ compensation benefits being claimed. The agency uses the form to open a dispute file, route the matter for mediation or hearing, and track statutory compliance.

Every Michigan employer that carries workers’ compensation insurance, every authorized self-insured employer, and every workers’ compensation insurance carrier or third-party administrator (TPA) acting on the employer’s behalf has authority to file. In practice, claims adjusters at carriers and TPAs file the bulk of these notices, while small self-insured employers and defense attorneys file the rest. The injured worker does not file WC-105; workers use Form WC-117 (Application for Mediation or Hearing) when they want to push a denied claim into litigation.

The form interacts with several related filings. The Form WC-100 (Employer’s Basic Report of Injury) opens the claim file. The Form WC-701 (Notice of Compensation Payments) reports voluntary payment. WC-105 is the document that tells the agency the carrier has decided not to pay, or has decided to stop paying, and explains why.

Before You Start: Documents and Information You Need

Filing WC-105 without the right paperwork in front of you almost always leads to a rejected or amended notice. The “Reason for Dispute” box is short, but the facts behind it must be airtight, because a magistrate can later impose penalties under MCL 418.801(2) if the dispute is found to be without reasonable grounds.

Gather these items before you open the form:

• The employer’s full legal name and FEIN, because a name mismatch with the WC-100 will cause the agency to reject the filing as a stray document.
• The insurance carrier name and NAIC code, since the agency cross-references the carrier against its proof of coverage database.
• The claim number assigned by the carrier or TPA, because without it, the agency cannot link the dispute to the correct claim file.
• The injured worker’s full legal name, Social Security number, and date of birth, because SSN mismatches block electronic indexing.
• The date of injury and date of disability, which often differ and must each be entered correctly to preserve later defenses.
• A copy of the WC-100 already filed, so the dispute facts line up with the report of injury.
• Any medical reports, IME findings, or surveillance you intend to rely on, because the dispute reason must be supported by evidence in the file.
• The average weekly wage (AWW) calculation worksheet under MCL 418.371, if wage rate is part of the dispute.
• The adjuster’s or attorney’s contact information and signature authority, since an unsigned WC-105 is treated as not filed.
• Proof of the mailing or service address for the injured worker and any known attorney of record, because the form requires a sworn proof of service.

Where to Get the Form and How to Access It

The official, current version of Form WC-105 lives on the agency’s WDCA forms page under the Department of Labor and Economic Opportunity. The form is a fillable PDF that filers can complete on screen, print, sign, and submit. Always download a fresh copy for each filing, because the agency updates the form when the WDCA administrative rules or statute change.

Carriers and TPAs that file in volume can use the WDCA electronic filing system to upload the completed PDF directly into the agency claim file. Smaller filers usually print the form, sign in ink, and send it by U.S. mail or commercial carrier. Walk-in filing is also accepted at the agency’s Lansing office.

If you cannot access the PDF, the WDCA Customer Service line at (888) 396-5041 will mail a paper copy on request. Defense law firms typically keep a stocked supply because turnaround on disputes is short. Never use a photocopied form pulled from an old claim file, because outdated revisions get rejected for missing the current authority block.

Step-by-Step: How to Fill Out Form WC-105 Line by Line

The walkthrough below moves through the form in the order the boxes appear. Each field gets its own subsection so you can match what you see on screen to the instruction here. The form is short, but every box matters, because the agency keys data straight into the claim management system.

Heading: Authority, Completion, and Penalty Block

The top of the form lists the statutory authority (P.A. 317 of 1969, as amended), states that completion is mandatory, and warns that penalties apply for false statements. Read this block once before you fill anything in, because it sets the legal weight of the entire document. Do not write in this area; it is informational only.

For example, Maria Lopez, a senior claims examiner at a Michigan TPA, reviews the heading every time she opens a fresh PDF to confirm she has the current revision. A nuance worth noting is that the heading also identifies the form as a public record once filed, which means anything written below can be obtained by subpoena. The most common mistake here is ignoring the penalty language and treating the form as informal correspondence; the consequence is that careless or misleading entries can support a bad-faith finding under MCL 418.801(2). A frequent misconception is that the heading is boilerplate that does not bind the filer, when in fact it is the legal anchor for everything that follows.

Box 1: WDCA Claim Number

This box asks for the claim number the WDCA assigned when the WC-100 was filed. Enter the number exactly as it appears on the agency’s acknowledgment, with no extra spaces or dashes. For example, Maria Lopez writes 2026-114578 in this box for a claim her TPA opened earlier in the year.

The nuance is that some claims have not yet received a WDCA number when the carrier needs to dispute, especially when the dispute is filed quickly after a late-reported injury. In that case, leave the box blank and write PENDING in light pencil to flag it for the intake clerk, and the agency will assign a number on receipt. The most common mistake is entering the carrier’s internal claim number instead of the WDCA number, which causes the dispute to be filed as a new matter and orphaned from the existing claim. A widespread misconception is that the WDCA claim number and the carrier claim number are the same; they are not, and confusing them is the single most common cause of misrouted disputes.

Box 2: Carrier or Self-Insurer Claim Number

This box captures the internal claim number used by the insurance carrier, TPA, or self-insured employer. Enter the number exactly as it appears in the claim system, including any letter prefixes. Maria Lopez writes WC-MI-2026-00917 to match her TPA’s file.

The nuance is that some self-insured employers do not assign claim numbers and instead use the worker’s employee ID; in that case, write the employee ID and add (EE ID) in parentheses. The most common mistake is leaving this box blank because the filer assumes the WDCA number alone is enough; the consequence is that the carrier’s own claim system cannot reconcile the dispute when the agency’s confirmation comes back. A misconception is that this number is optional; the agency treats it as required for cross-referencing under Rule 418.31.

Box 3: Employee Name

Enter the injured worker’s full legal name in the order Last, First, Middle. Use the name that appears on the Social Security card and the WC-100, because the agency cross-checks both. Maria Lopez writes Carter, James R. for her disputed claim.

A nuance arises when the worker has changed names since the injury, for example through marriage or divorce; in that case, use the name on the WC-100 and add the current name in parentheses. The most common mistake is writing a nickname or shortened first name, which causes the SSN-name match to fail and delays indexing. A misconception is that small spelling differences do not matter; in practice, Jim instead of James can hold up a filing for days while a clerk requests correction.

Box 4: Employee Social Security Number

Enter the worker’s nine-digit SSN in the format XXX-XX-XXXX. Confirm the number against the WC-100 before you write it down. Maria Lopez writes 380-44-7129 in this box.

The nuance is that workers without a valid SSN, including some undocumented workers and certain seasonal workers, may have an Individual Taxpayer Identification Number (ITIN); in that case, enter the ITIN and write (ITIN) next to it. The most common mistake is transposing two digits, which causes the agency’s electronic match to fail and the dispute to sit in a manual review queue. A common misconception is that the SSN can be redacted on the public copy; on the agency copy it must be complete, though carriers often serve a redacted copy on the worker for privacy.

Box 5: Date of Injury

Enter the date the injury occurred, or for occupational diseases, the date of last injurious exposure, in MM/DD/YYYY format. This date controls the statute of limitations under MCL 418.381. Maria Lopez writes 01/14/2026.

A nuance is that for repetitive trauma claims like carpal tunnel, the “date of injury” is treated as the last day worked in the injurious employment, not the day symptoms began. The most common mistake is entering the date the worker first reported the injury, which is often weeks later and creates a defensible-but-confusing record. A misconception is that this date is flexible; it is not, and Michigan magistrates treat the date of injury as the anchor for nearly every other deadline in the case.

Box 6: Employer Name and FEIN

Enter the employer’s full legal name exactly as registered with the Michigan Department of Treasury and the nine-digit Federal Employer Identification Number. Maria Lopez writes Great Lakes Logistics, Inc., FEIN 38-2211009.

The nuance is that staffing arrangements often involve a host employer and a staffing agency, and the WC-105 must name the legal employer of record for workers’ compensation purposes, which is usually the staffing agency. The most common mistake is using a “doing business as” name instead of the legal name, which breaks the proof of coverage match. A misconception is that the FEIN is optional for small employers; it is required, and using a Social Security number in its place will cause the filing to be rejected.

Box 7: Insurance Carrier Name and NAIC Code

Enter the insurance carrier’s full legal name and five-digit NAIC code. Self-insured employers write SELF-INSURED and enter their WDCA self-insurer ID. Maria Lopez writes Midwest Indemnity Insurance Co., NAIC 14582.

A nuance is that excess carriers above a self-insured retention should not be listed here; only the entity legally responsible for the first-dollar defense belongs in this box. The most common mistake is naming the TPA instead of the carrier, which is a frequent source of confusion because the TPA’s logo is on the adjuster’s letterhead. A misconception is that the NAIC code is interchangeable with the carrier’s Michigan insurance license number; the agency’s matching system uses NAIC, and a license number entered here will fail validation.

Box 8: Date Disability Began

Enter the first date the worker became disabled from work, in MM/DD/YYYY format. This date is often different from the date of injury and controls when wage-loss benefits would have begun under MCL 418.301. Maria Lopez writes 01/17/2026, three days after the injury date she entered in Box 5.

The nuance is that for claims involving only medical benefits with no lost time, write NONE in this box; do not leave it blank. The most common mistake is copying the date of injury into this box by reflex, which suggests the worker missed work the same day and creates an inconsistency with the WC-100. A misconception is that the seven-day waiting period under MCL 418.311 gets entered here; it does not, and conflating the two will undermine your wage-rate defense.

Box 9: Average Weekly Wage

Enter the AWW calculated under MCL 418.371, using the highest 39 of the 52 weeks before the injury. Round to the nearest cent. Maria Lopez writes $1,142.83 based on the wage statement in her file.

A nuance is that workers with fewer than 39 weeks of employment require a different calculation that uses the actual weeks worked or, for very new hires, the wage of a similarly situated employee. The most common mistake is using gross weekly earnings averaged across all 52 weeks, which understates AWW and is one of the most frequently disputed errors at trial. A misconception is that overtime and discretionary bonuses are excluded; they are included if they were part of the worker’s regular earnings during the relevant period.

Box 10: Type of Dispute

Check the box or boxes that match the dispute. The choices typically include No Injury Arising Out of and in the Course of Employment, No Disability, Wage Rate Disputed, Medical Treatment Disputed, Notice/Claim Not Timely, and Other. Maria Lopez checks Wage Rate Disputed and Medical Treatment Disputed for her file.

The nuance is that you may check more than one box, and you should check every basis you intend to raise, because a basis not flagged here can be challenged later as waived. The most common mistake is checking Other without specifying anything, which a magistrate may treat as no notice at all under the reasoning of Brackett v. Focus Hope, 482 Mich 269 (2008). A misconception is that checking too many boxes weakens the defense; in Michigan practice, comprehensive flagging is preferred to narrow flagging.

Box 11: Reason for Dispute (Narrative)

Write a clear, fact-specific explanation of why benefits are disputed. Use plain language, name the medical or wage facts you rely on, and reference any IME or surveillance by date. Maria Lopez writes IME by Dr. R. Patel on 02/12/2026 found no objective evidence of work-related lumbar pathology; pre-existing degenerative disc disease documented in 2022 MRI. AWW recalculated from corrected payroll records reduces to $1,142.83.

The nuance is that the magistrate reads this box first at mediation, so vague language like claim not compensable invites a bad-faith finding under MCL 418.801(2). The most common mistake is using boilerplate copied from a prior claim, which a sharp claimant’s attorney will turn into a credibility argument. A misconception is that this box should be brief to avoid commitment; in fact, the more specific the narrative, the stronger the defense, and the agency expects detail proportional to the complexity of the dispute.

Box 12: Adjuster or Authorized Representative Signature

The person with claim authority must sign in ink, or apply a verified electronic signature if filing through the WDCA online services portal. Print the signer’s name and title below the signature. Maria Lopez signs and prints Maria Lopez, Senior Claims Examiner.

A nuance is that the signer must have authority to bind the carrier or self-insurer; signatures by clerical staff have been rejected. The most common mistake is a missing or illegible signature, which causes the agency to treat the form as not filed and start the late-filing penalty clock running. A misconception is that a typed name in the signature line satisfies the requirement on a paper filing; it does not, and only ink or a verified e-signature meets the standard.

Box 13: Date Signed

Enter the date the form was signed, in MM/DD/YYYY format. This date should match the date the form is mailed or uploaded. Maria Lopez writes 03/04/2026.

A nuance is that backdating this entry is a serious problem, because it can be used to cover a missed 14-day deadline and amounts to a false statement on a public record. The most common mistake is forgetting to update this date when a form is held overnight for review, which creates a paper-trail gap. A misconception is that the signature date and the date of mailing can be days apart without consequence; they should match within one business day to support timely filing.

Box 14: Proof of Service

Enter the names and addresses of the injured worker and any attorney of record served with a copy, the method of service, and the date of service. Maria Lopez writes James R. Carter, 1402 Maple St., Flint MI 48503, served by First-Class U.S. Mail on 03/04/2026; Attorney Linda Park, Park Law PLLC, 220 Court St., Detroit MI 48226, served by First-Class U.S. Mail on 03/04/2026.

The nuance is that service must reach the worker and the attorney of record on or before the agency filing date, and the proof of service must be sworn under penalty of perjury. The most common mistake is serving the worker but not the attorney, which can be treated as no service at all when an attorney has appeared. A misconception is that email service alone satisfies the rule; under WDCA administrative rules, email service requires prior written consent from the served party.

Three Filled-Out Examples Using Real Scenarios

The three scenarios below show how different filers move through the same form. Each table has eight rows mapped to the most important fields. Use these as templates, not as substitutes for your own facts.

Scenario 1: Carrier Disputes Compensability After IME

Devon Bell, a senior adjuster at a national carrier, disputes a back claim after an independent medical exam finds no work-related pathology.

Form Section	What Devon Enters
Box 1: WDCA Claim Number	2026-118402
Box 3: Employee Name	Carter, James R.
Box 5: Date of Injury	01/14/2026
Box 8: Date Disability Began	01/17/2026
Box 9: Average Weekly Wage	$1,242.10
Box 10: Type of Dispute	No Injury Arising Out of Employment
Box 11: Reason for Dispute	IME by Dr. Patel 02/12/2026 found no work-related lumbar pathology
Box 14: Proof of Service	Worker and Attorney Park served by U.S. Mail 03/04/2026

Scenario 2: Self-Insured Employer Disputes Wage Rate

Aisha Reed, HR director at a self-insured Michigan manufacturer, accepts compensability but disputes the AWW used for benefit calculation.

Form Section	What Aisha Enters
Box 2: Self-Insurer Claim Number	GLM-2026-0042
Box 6: Employer Name and FEIN	Great Lakes Manufacturing, Inc., 38-1100447
Box 7: Insurance Carrier	SELF-INSURED, WDCA SI-0117
Box 8: Date Disability Began	02/02/2026
Box 9: Average Weekly Wage	$986.40
Box 10: Type of Dispute	Wage Rate Disputed
Box 11: Reason for Dispute	Corrected payroll excludes one-time signing bonus per MCL 418.371
Box 14: Proof of Service	Worker served by certified mail 02/20/2026

Scenario 3: TPA Disputes Continuing Disability After Surveillance

Marcus Tanaka, a TPA adjuster, accepts the original injury but disputes ongoing disability after surveillance video shows the worker performing physical labor inconsistent with restrictions.

Form Section	What Marcus Enters
Box 1: WDCA Claim Number	2025-091877
Box 3: Employee Name	Nguyen, Thanh L.
Box 5: Date of Injury	08/03/2025
Box 8: Date Disability Began	08/04/2025
Box 10: Type of Dispute	No Disability; Medical Treatment Disputed
Box 11: Reason for Dispute	Surveillance 01/22/2026 shows roofing work; IME 02/05/2026 releases to full duty
Box 12: Signature	Marcus Tanaka, Senior Adjuster
Box 14: Proof of Service	Worker and Attorney Diaz served by U.S. Mail 02/18/2026

How to File the Completed Form

Michigan accepts WC-105 through several channels, and the right channel depends on the filer’s volume and access. Carriers and TPAs that handle many claims should use the WDCA online filing system, which timestamps the upload, returns an instant confirmation, and routes the document into the agency claim file the same business day. There is no filing fee.

Paper filers mail the signed original to Workers’ Disability Compensation Agency, P.O. Box 30016, Lansing, MI 48909. Use First-Class U.S. Mail with a Certificate of Mailing or commercial overnight service, because Michigan applies the mailbox rule under Rule 418.41 and a date-stamped mailing receipt is the filer’s best proof of timeliness. Walk-in filing is accepted at 2501 Woodlake Circle, Okemos, MI 48864 during regular business hours.

Fax filing at (517) 636-0133 is accepted in limited circumstances, usually when a deadline is imminent and online access is unavailable; always follow a fax filing with a mailed original. There is no filing fee through any channel. Keep the agency confirmation, the certified mail receipt, or the fax confirmation page in the claim file as proof of filing, because the burden of proving timely filing falls on the filer in any later penalty hearing.

What Happens After You File

Once the agency receives the WC-105, the document is indexed against the existing claim file and the worker is treated as having a disputed claim for purposes of the WDCA mediation and hearing process. The worker may then file a Form WC-117 to request mediation or a hearing before a workers’ compensation magistrate. In practice, most disputed claims move into mediation within 60 to 120 days of the WC-105 filing.

Mediation is informal and non-binding, and the magistrate or mediator will read the WC-105 narrative carefully when assessing the strength of each side’s case. If mediation does not resolve the dispute, the case proceeds to a formal hearing where live testimony, medical depositions, and exhibits are presented. A magistrate’s decision can be appealed to the Michigan Compensation Appellate Commission within 30 days.

If the magistrate ultimately rules that benefits should have been paid and that the dispute lacked reasonable grounds, the carrier or self-insurer can be ordered to pay the underlying benefits, statutory interest under MCL 418.801(6), a 50-percent penalty on overdue weekly benefits, and the worker’s attorney fees. These consequences are why the narrative in Box 11 must always be specific, supported, and signed by a person with claim authority.

Mistakes to Avoid When Filling Out the Form

The following errors appear most often in WC-105 filings and each one carries a direct consequence in the claim file or at hearing.

• Writing the carrier claim number in Box 1 instead of the WDCA claim number, which orphans the dispute from the existing claim file.
• Leaving Box 2 blank, which prevents the carrier system from reconciling the agency confirmation back to the internal file.
• Using a nickname in Box 3, which causes the agency’s name-SSN match to fail and delays indexing.
• Transposing two digits in the SSN at Box 4, which sends the filing to a manual review queue for days.
• Entering the report date instead of the injury date in Box 5, which can shift the statute of limitations analysis.
• Naming the staffing agency’s client in Box 6 instead of the legal employer of record, which breaks the proof of coverage match.
• Listing the TPA in Box 7 instead of the insurance carrier, which fails NAIC validation.
• Copying the date of injury into Box 8, which suggests same-day disability and contradicts the WC-100.
• Calculating AWW from a flat 52-week average in Box 9, which understates the wage and invites a magistrate adjustment with penalties.
• Checking only Other in Box 10 without specifying, which a magistrate may treat as no notice.
• Writing boilerplate in Box 11, which can support a bad-faith finding under MCL 418.801(2).
• Skipping the ink signature in Box 12, which causes the form to be treated as not filed.
• Failing to serve the attorney of record in Box 14, which can be treated as no service.

Do’s and Don’ts

These rules of thumb come from years of WDCA practice and reflect what magistrates actually look for.

• Do download a fresh PDF from the agency for each filing, because revisions change without broad notice.
• Do match every name and number on the form to the WC-100 and the proof of coverage, because mismatches are the leading cause of rejection.
• Do write a fact-specific narrative in Box 11, because magistrates read it first.
• Do keep the proof of mailing or upload confirmation in the claim file, because timeliness is the filer’s burden to prove.
• Do serve the attorney of record at the same time as the worker, because partial service is treated as no service.
• Do sign in ink or with a verified e-signature, because typed names on paper filings are rejected.
• Don’t backdate the signature line, because doing so is a false statement on a public record.
• Don’t use boilerplate from a prior claim, because reused language undermines credibility at mediation.
• Don’t check only Other in Box 10, because the magistrate needs a specific basis to rule on.
• Don’t wait past the 14-day window in MCL 418.801(1), because the late-payment penalty starts to accrue automatically.
• Don’t assume email service satisfies the proof of service rule, because written consent is required.
• Don’t treat the form as informal correspondence, because it is a sworn document on a public record.

Pros and Cons of Filing on Your Own vs. With Help

Carriers, TPAs, and self-insured employers must decide whether to handle WC-105 in house or through outside defense counsel.

Pros of filing in house:

• Faster turnaround, because the adjuster who knows the file can sign and file the same day.
• Lower cost, because no outside legal fees are incurred for routine disputes.
• Better claim continuity, because the adjuster’s narrative reflects the file as it is being managed.
• Easier coordination with the WC-100 and WC-701 already on file with the agency.
• Direct ownership of the dispute strategy from day one of the claim.

Cons of filing in house:

• Higher risk of vague Box 11 narratives, because adjusters may default to internal shorthand.
• Greater exposure to bad-faith findings if the dispute is later judged unreasonable.
• Less ability to anticipate magistrate-specific preferences across Michigan’s hearing sites.
• Reduced leverage in mediation when the worker is represented by experienced claimant’s counsel.
• Limited ability to coordinate the WC-105 with later motions and discovery strategy.

FAQs

Is there a filing fee for Form WC-105?

No. The Michigan WDCA does not charge a filing fee for the Notice of Dispute, regardless of whether the form is submitted online, by mail, by fax, or in person at the Okemos office.

How long do I have to file WC-105 after a claim is reported?

No single deadline governs every dispute, but the form should reach the agency within 14 days of the date the first compensation payment would have been due under MCL 418.801(1) to avoid late-payment penalties.

Can the injured worker file Form WC-105?

No. The Notice of Dispute is filed by the employer, carrier, TPA, or self-insurer; injured workers use Form WC-117 to request mediation or a hearing on a denied claim.

Do I write the WDCA claim number or the carrier claim number in Box 1?

Yes for the WDCA claim number; Box 1 is for the agency-assigned number, while the carrier or self-insurer number goes in Box 2 to avoid orphaning the dispute.

Can I leave Box 8 (Date Disability Began) blank for a medical-only claim?

No. Write NONE in Box 8 when the claim involves only medical benefits, because a blank box is treated as an incomplete filing.

Should overtime be included in the AWW entered in Box 9?

Yes. Regular overtime and bonuses paid during the 52 weeks before injury are included in the highest-39-week calculation under MCL 418.371.

Can I check more than one box in Box 10?

Yes. Check every basis you intend to raise, because a basis not flagged on the WC-105 can be challenged later as waived under Michigan workers’ compensation practice.

Is a typed name acceptable as a signature in Box 12?

No for paper filings; only ink signatures or verified electronic signatures through the WDCA online portal satisfy the signature requirement.

Does email service to the worker satisfy Box 14?

No unless the served party has given prior written consent to email service under the WDCA administrative rules.

Can I file WC-105 by fax?

Yes in limited situations when a deadline is imminent, but the fax filing should always be followed by a mailed original to preserve the record.

Will a vague Reason for Dispute in Box 11 cause a problem?

Yes. Vague or boilerplate language can support a bad-faith finding under MCL 418.801(2), which exposes the carrier to penalties, interest, and attorney fees.

Do I need to file a new WC-105 if the basis for the dispute changes?

Yes. File an amended WC-105 promptly when new facts, IME findings, or surveillance change the basis for the dispute, because the agency tracks each filing as a separate event in the claim file.

Can I file WC-105 before filing the WC-100?

No. The WC-100 (Employer’s Basic Report of Injury) must be on file first, because the WC-105 attaches to the existing claim and cannot exist without one.

What happens if the agency rejects my WC-105 for a missing field?

Yes, rejection is common; the agency returns the form with a deficiency notice, and the filer must correct and refile, while any statutory deadlines continue to run during the correction period.