How to Enter Secondary Medigap Insurance on CMS-1500 Medicare Claims

How to Enter Secondary Medigap Insurance on CMS-1500 Medicare Claims

Mastering how to enter secondary Medigap insurance on CMS-1500 Medicare claims is a critical skill for any medical billing professional. Accurate Medigap billing ensures timely reimbursement for providers and prevents unexpected out-of-pocket costs for patients, fostering trust and financial stability within your practice. While Medicare acts as the primary payer for beneficiaries, Medigap plans step in to cover the gaps – deductibles, coinsurance, and sometimes excess charges – that Medicare doesn’t. Incorrectly submitting these claims can lead to frustrating denials, delayed payments, and increased administrative burden. This comprehensive guide will walk you through the intricacies of Medigap claim submission, from understanding the nuances of the CMS-1500 form to navigating electronic data interchange (EDI) and troubleshooting common denial scenarios. We’ll delve into specific field-by-field instructions, provide real-world examples, and equip you with the expert knowledge needed to streamline your Medigap billing process. —

Quick Reference Guide: CMS-1500 Fields for Medigap Claims

This table provides a concise overview of the most critical fields on the CMS-1500 form when billing secondary Medigap insurance. Refer to this guide for quick answers, then dive into the detailed breakdown for in-depth explanations and examples.

Field Number	Field Name	Medigap Specific Instruction	Key Takeaway
1a	Insured’s ID Number	Enter the patient’s Medicare Beneficiary Identifier (MBI).	Always the MBI for Medicare primary.
9	Other Insured’s Name	Enter the Medigap policyholder’s name (Last Name, First Name, Middle Initial). This is often the patient themselves.	Crucial for identifying the Medigap policy.
9a	Other Insured’s Policy or Group Number	Enter the Medigap policy number. Do NOT include the Medicare MBI here.	The unique identifier for the Medigap plan.
9b	Reserved for NUCC Use	Leave blank.	No data entry required.
9c	Employer’s Name or School Name	Leave blank for Medigap.	Not applicable for Medigap.
9d	Insurance Plan Name	Enter the full name of the Medigap plan (e.g., “AARP Medicare Supplement Plan F”).	Be precise with the plan name.
11	Insured’s Policy, Group, or FECA Number	Enter “NONE” or leave blank if Medicare is the only primary. If there’s another primary payer before Medicare, enter that policy number here.	This field is for the primary payer’s policy number.
11a	Insured’s Date of Birth	Enter the primary insured’s DOB. For Medigap, this is the patient’s DOB.	Patient’s DOB.
11c	Insurance Plan Name	Enter “MEDICARE”.	Identifies Medicare as the primary.
13	Insured’s or Authorized Person’s Signature	Enter “SIGNATURE ON FILE” or “SOF” if you have a valid assignment of benefits on record.	Ensures payment goes to the provider.
29	Amount Paid	Enter the amount Medicare paid on the primary claim. This is crucial for Medigap to calculate its responsibility.	Reflects Medicare’s payment.
30	Balance Due	Enter the remaining balance after Medicare’s payment. This is what Medigap is expected to cover.	The amount Medigap should pay.

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Detailed Breakdown: Mastering Medigap Claim Submission

Successfully billing Medigap insurance requires a deep understanding of its relationship with Medicare and meticulous attention to detail on the CMS-1500 form. This section will provide an exhaustive guide, addressing common challenges and best practices for both paper and electronic submissions.

Understanding Medigap and Medicare Crossover Claims

Medigap, also known as Medicare Supplement Insurance, is private health insurance designed to pay for healthcare costs that Original Medicare (Part A and Part B) doesn’t cover. These “gaps” typically include deductibles, coinsurance, and copayments. It’s crucial to understand that Medigap plans only work with Original Medicare, not with Medicare Advantage (Part C) plans.

Medicare Part A: Covers inpatient hospital stays, skilled nursing facility care, hospice care, and some home health care. Medigap can cover the Part A deductible and coinsurance.

Medicare Part B: Covers certain doctors’ services, outpatient care, medical supplies, and preventive services. Medigap can cover the Part B deductible, coinsurance (typically 20% of the Medicare-approved amount), and sometimes Part B excess charges (if the provider doesn’t accept Medicare assignment).

When a patient has both Original Medicare and a Medigap policy, the billing process typically follows a “crossover” mechanism.

Automatic Crossover: In most cases, after Medicare processes a claim and pays its portion, it automatically forwards (crosses over) the claim information to the patient’s Medigap insurer. This is the most efficient method and requires no additional action from the provider’s billing team. However, not all Medigap plans participate in automatic crossover, or sometimes the crossover fails due to incorrect information on file.

Manual Submission: If a claim does not automatically cross over, or if the Medigap plan is not set up for crossover, the provider must manually submit the claim to the Medigap insurer. This is where accurate completion of the CMS-1500 form becomes paramount.

Navigating the CMS-1500 Form for Medigap

When submitting a paper claim to a Medigap insurer, you’ll use the CMS-1500 form. The key is to correctly identify Medicare as the primary payer and the Medigap plan as the secondary.

Item 1a: Insured’s ID Number

Instruction: Always enter the patient’s Medicare Beneficiary Identifier (MBI) here. This is the 11-character alphanumeric ID found on the patient’s Medicare card.

Why it matters: This field links the claim to the patient’s primary Medicare coverage.

Item 9: Other Insured’s Name (The Crucial Field)

This is arguably the most critical field for Medigap claims. It identifies the Medigap policyholder.

Instruction: Enter the full name of the Medigap policyholder: Last Name, First Name, Middle Initial.

Specific Example 1: Patient is the Medigap Policyholder

If John A. Doe is the patient and also holds the Medigap policy, you would enter: `DOE, JOHN A`

Specific Example 2: Spouse is the Medigap Policyholder

If Jane B. Smith is the patient, but her husband, Robert C. Smith, holds the Medigap policy, you would enter: `SMITH, ROBERT C`

Important: In this scenario, you would also need to indicate the relationship in Item 10d (if applicable, though often left blank for Medigap) and ensure Item 11a (Insured’s DOB) reflects the patient’s* DOB, not the spouse’s, as the patient is the one receiving services.

Specific Example 3: Deceased Policyholder

If the Medigap policyholder is deceased, but the policy is still active for the patient (e.g., a surviving spouse), enter the deceased policyholder’s name. Be prepared to provide additional documentation if requested by the Medigap insurer.

Common Error: Entering “SAME” or leaving this field blank when a manual submission is required. This will lead to a denial.

Item 9a: Other Insured’s Policy or Group Number

Instruction: Enter the specific policy number for the Medigap plan. This is not* the Medicare MBI. It’s a unique number assigned by the Medigap insurer.

Why it matters: This number directly links the claim to the patient’s Medigap policy.

Common Error: Entering the Medicare MBI again, or an incorrect/expired Medigap policy number. Always verify this number from the patient’s Medigap card or through eligibility verification.

Item 9d: Insurance Plan Name (Medigap Plan Name)

Instruction: Enter the full, accurate name of the Medigap insurance plan.

Example: “AARP Medicare Supplement Plan F,” “Blue Cross Blue Shield Medigap Plan G,” “UnitedHealthcare Medicare Supplement Plan N.”

Why it matters: Precision here helps the Medigap insurer quickly identify the correct plan and process the claim. Abbreviations or generic terms can cause delays.

Item 11: Insured’s Policy, Group, or FECA Number

Instruction: This field is for the primary insurance policy number. Since Medicare is primary, and its ID is in Item 1a, you typically enter “NONE” or leave this field blank for Medigap claims. If there was another primary payer before* Medicare (e.g., a large group health plan), that policy number would go here.

Why it matters: Clarifies the primary payer status.

Item 11c: Insurance Plan Name (Primary)

Instruction: Enter “MEDICARE.”

Why it matters: Explicitly states Medicare as the primary insurer.

Item 13: Insured’s or Authorized Person’s Signature

Instruction: Enter “SIGNATURE ON FILE” or “SOF” if you have a valid assignment of benefits on record. This authorizes the Medigap insurer to pay the provider directly.

Why it matters: Without this, payment might go to the patient, causing collection issues for the provider.

Item 29: Amount Paid

Instruction: After Medicare has processed the primary claim, enter the exact amount Medicare paid. This information is found on the Medicare Remittance Advice (RA) or Explanation of Benefits (EOB).

Why it matters: Medigap uses this figure to calculate its secondary payment responsibility.

Common Error: Leaving this blank or entering the total charges.

Item 30: Balance Due

Instruction: Enter the remaining balance after Medicare’s payment. This is the amount Medigap is expected to cover (e.g., deductible, coinsurance, excess charges).

Why it matters: Clearly indicates the amount the secondary payer is responsible for.

Electronic Claim Submission (EDI) for Medigap

While paper claims are still used, electronic claim submission (EDI) via the 837P transaction set is the prevalent and most efficient method for submitting Medigap claims. EDI significantly reduces processing time, minimizes errors, and improves cash flow.

Advantages of EDI:

Faster Processing: Claims are received and processed much quicker than paper.

Reduced Errors: Clearinghouse scrubbers identify common errors before submission.

Cost-Effective: Eliminates printing, postage, and manual data entry.

Improved Tracking: Easier to monitor claim status.

Key Data Elements in 837P for Medigap:

Loop 2320 (Other Subscriber Information): This loop contains details about the Medigap policyholder.

SBR01 (Payer Responsibility Sequence Number Code): Typically “S” for secondary.

SBR02 (Individual Relationship Code): “18” for self, “01” for spouse, etc.

SBR03 (Reference Identification): The Medigap policy number.

SBR04 (Insurance Type Code): “MB” for Medigap.

Loop 2330B (Other Payer Information): This loop identifies the Medigap payer itself.

NM101 (Entity Identifier Code): “PR” for Payer.

NM103 (Payer Name): Full name of the Medigap insurer.

NM109 (Payer Identifier): The Medigap Payer ID (a unique identifier for electronic routing).

REF02 (Policy Number): The Medigap policy number.

AMT (Amount Paid): The amount Medicare paid on the primary claim.

DTP (Date): Date of Medicare’s payment.

CAS (Claim Adjustment Segment): Details from Medicare’s RA/EOB (e.g., deductible, coinsurance amounts).

Medicare Crossover vs. Direct Medigap Submission (EDI):

Automatic Crossover (EDI): When Medicare automatically forwards the claim, the provider doesn’t submit a separate 837P to the Medigap plan. Medicare handles the electronic transfer.

Direct Medigap Submission (EDI): If crossover fails or isn’t supported, the provider submits a secondary 837P claim directly to the Medigap insurer via their clearinghouse. This claim must* include the Medicare payment information (Loop 2320/2330B details) to ensure proper adjudication.

Importance of Accurate Payer IDs: Just as with paper claims, the correct Payer ID for the Medigap insurer is essential for electronic routing. Verify these with your clearinghouse or the Medigap insurer directly.

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Real-World Billing Scenarios & Patient Status Changes

Understanding the theory is one thing; applying it to diverse patient situations is another. Here are several common scenarios you might encounter when billing Medigap.

Scenario 1: Standard Medigap Claim (Patient has Plan F)

Patient: Mary Johnson, 72 years old. Primary Insurance: Original Medicare. Secondary Insurance: AARP Medicare Supplement Plan F (Medigap). Service: Office visit, $150.00. Medicare Payment: Medicare pays 80% of the approved amount after the Part B deductible is met. Let’s assume the deductible is met, and Medicare approved $100.00. Medicare pays $80.00. Medigap Responsibility: Plan F covers the remaining 20% coinsurance ($20.00) and any Part B deductible (if not met). Billing Steps: 1. Submit to Medicare (Primary): Bill the $150.00 to Medicare. 2. Receive Medicare RA/EOB: Medicare pays $80.00. The RA shows a $20.00 coinsurance. 3. Prepare Secondary Claim for Medigap:

Item 1a: Mary Johnson’s MBI.

Item 9: `JOHNSON, MARY` (assuming Mary is the policyholder).

Item 9a: Mary’s AARP Medigap policy number.

Item 9d: `AARP MEDICARE SUPPLEMENT PLAN F`.

Item 11c: `MEDICARE`.

Item 29: `$80.00` (Medicare’s payment).

Item 30: `$20.00` (Balance due from Medigap).

Item 24J: Rendering provider NPI.

Item 33: Billing provider information.

4. Submit to AARP Medigap: Either via automatic crossover (if applicable) or manual submission.

Scenario 2: Medigap with Medicare Advantage (MA) Plan (Not a True Medigap)

Patient: Robert Davis, 68 years old. Insurance Cards Presented:

Medicare Advantage card (e.g., Humana Gold Plus HMO).

A card labeled “Medicare Supplement” (e.g., Blue Cross Blue Shield Medigap Plan G).

Action: This is a critical point of confusion. Medigap plans cannot be used with Medicare Advantage plans. Medicare Advantage plans are an alternative to Original Medicare, and they bundle Part A, Part B, and often Part D benefits. If a patient has an MA plan, their Medigap policy is essentially void or should have been canceled. Billing Steps: 1. Educate the Patient: Explain that they cannot have both. They must choose between Original Medicare + Medigap OR a Medicare Advantage plan. 2. Verify Enrollment: Contact the MA plan to confirm active enrollment. If active, the MA plan is the only payer. 3. Do NOT Bill Medigap: Only bill the Medicare Advantage plan. The “Medigap” card is irrelevant in this scenario. 4. Advise Patient: Strongly recommend the patient contact their insurance agent or Medicare to clarify their coverage and potentially cancel the redundant Medigap policy to avoid unnecessary premiums.

Scenario 3: Patient has Medigap and another Commercial Secondary

Patient: Sarah Lee, 67 years old. Primary Insurance: Original Medicare. Secondary Insurance 1: Employer-sponsored group health plan (e.g., Cigna). Secondary Insurance 2: UnitedHealthcare Medicare Supplement Plan G (Medigap). Coordination of Benefits (COB) Order: Medicare’s COB rules dictate the payment order. Generally, for patients over 65 with employer-sponsored coverage, Medicare is primary if the employer has fewer than 20 employees. If the employer has 20 or more employees, the employer plan is primary. For this scenario, let’s assume Medicare is primary. The order would be: Medicare -> Cigna (Commercial Secondary) -> UnitedHealthcare Medigap (Tertiary). Billing Steps: 1. Submit to Medicare (Primary): Bill the full charges to Medicare. 2. Receive Medicare RA/EOB: Note Medicare’s payment and any remaining balance (deductible, coinsurance). 3. Submit to Cigna (Secondary):

Use the CMS-1500 form.

Item 11: Enter “MEDICARE” and the patient’s MBI in Item 1a.

Item 9: Enter the patient’s name (if Cigna policyholder).

Item 9a: Cigna policy number.

Item 9d: Cigna plan name.

Item 29: Medicare’s payment.

Item 30: Balance after Medicare.

4. Receive Cigna RA/EOB: Note Cigna’s payment and any remaining balance. 5. Submit to UnitedHealthcare Medigap (Tertiary):

Use the CMS-1500 form.

Item 1a: Sarah Lee’s MBI.

Item 9: `LEE, SARAH` (assuming Sarah is the policyholder).

Item 9a: Sarah’s UnitedHealthcare Medigap policy number.

Item 9d: `UNITEDHEALTHCARE MEDICARE SUPPLEMENT PLAN G`.

Item 11: Enter Cigna’s policy number

FAQ: Common Questions Answered

What is the difference between Medigap and Medicare Advantage plans for billing purposes?

This is a crucial distinction for billing professionals. Medigap (Medicare Supplement Insurance) plans work in conjunction with Original Medicare (Parts A & B). You bill Original Medicare first as the primary payer. Once Original Medicare processes the claim and pays its portion, Medigap then steps in as the secondary payer to cover the remaining patient responsibility, such as deductibles, coinsurance, and sometimes excess charges. For billing, this means submitting the claim to Medicare, receiving the Remittance Advice (RA), and then submitting the secondary claim to Medigap, often using specific fields on the CMS-1500 form to indicate the primary Medicare payment. Medicare Advantage (Part C) plans, however, are an alternative to Original Medicare. They are private insurance plans that replace Original Medicare. When a patient has a Medicare Advantage plan, you bill the Advantage plan directly as the primary payer. You do not bill Original Medicare at all. Medicare Advantage plans have their own networks, prior authorization requirements, and claim submission processes, which can differ significantly from Original Medicare and Medigap. Incorrectly identifying the plan type is a leading cause of denials and payment delays.

How do I handle Medigap claims when Medicare denies the primary claim?

If Original Medicare denies the primary claim, the Medigap plan will also deny it, as Medigap only covers costs after Medicare has processed and paid its portion, or determined patient liability for covered services. Your immediate priority is to address the Medicare denial. Review the Medicare Remittance Advice (RA) or Explanation of Benefits (EOB) thoroughly to understand the specific denial reason code. Common reasons include missing information, incorrect coding, lack of medical necessity, or timely filing issues. You must correct and resubmit the claim to Medicare, or initiate an appeal if appropriate. Only once Medicare has processed the claim, either by paying its portion or by determining the patient’s liability for a covered service, can the Medigap claim be successfully processed. Attempting to bill Medigap before the primary Medicare claim is resolved will result in a Medigap denial and increased administrative burden. If Medicare denies a service as “not covered,” Medigap typically will not cover it either, unless it falls under specific excess charge coverage or a unique benefit of the Medigap plan.

Are there specific Medigap plan types that require unique handling on the CMS-1500?

While the core process for billing Medigap as secondary insurance on the CMS-1500 remains largely consistent across all plans (A, B, C, D, F, G, K, L, M, N), there are subtle nuances. Medigap plans are standardized by law, meaning the benefits for a Plan G, for example, are the same regardless of the insurance company. Therefore, the fundamental fields on the CMS-1500 (like Field 1a for the MBI, and Fields 9/9a for Medigap policyholder info) are universally applied. However, some plans, such as Plan F and Plan G, cover Medicare Part B excess charges. If your provider charges above the Medicare-approved amount, and the patient has one of these plans, it’s crucial to ensure the claim accurately reflects the charges so the Medigap plan can cover the excess. While the CMS-1500 fields themselves don’t drastically change, the electronic data interchange (EDI) submission might require specific payer IDs for each Medigap insurer, even if the form fields are standard. It’s always best practice to verify the specific Medigap payer ID and any unique electronic submission requirements directly with the Medigap insurer to ensure smooth processing.

What are the most common reasons for Medigap claim rejections or delays?

Medigap claim rejections or delays typically stem from issues with either the primary Medicare claim or the Medigap policy information itself. The most common reasons include:

1. Primary Medicare Denial or Non-Payment: Medigap will not pay if Original Medicare has not processed the primary claim, or if Medicare denied the primary claim for reasons that preclude Medigap coverage (e.g., not medically necessary, non-covered service).
2. Incorrect Medigap Policy Information: Errors in Field 9 (Other Insured’s Name) or Field 9a (Other Insured’s Policy Number) on the CMS-1500 can prevent the Medigap insurer from identifying the policyholder.
3. Timely Filing Limits: Both Medicare and Medigap plans have strict timely filing limits. If the primary Medicare claim was filed late, or if the secondary Medigap claim is submitted too long after Medicare’s processing, it can be denied.
4. Missing or Incorrect Medicare EOB/RA: For paper claims, the Medigap insurer often requires a copy of the Medicare EOB/RA. For electronic claims, the crossover information from Medicare must be accurately transmitted.
5. Patient Responsibility Not Met: If the patient has not yet met their Medicare deductible, Medigap will not pay until that deductible is satisfied by Medicare’s processing.
6. Coordination of Benefits (COB) Issues: If there are other insurances involved (e.g., an employer group health plan), an incorrect COB order can lead to Medigap denying the claim as not the correct secondary payer.

Addressing these common pitfalls through meticulous data entry, timely submission, and thorough review of Medicare RAs is key to streamlining Medigap billing.

External Resources & Authority Links

• For more detailed insights, refer to the official CMS Medicare guidelines.
• For more detailed insights, refer to the CMS guidelines.