MSP Payment Calculator

This MSP Calculator is a tool to assist in determining the line by line claim payment calculations for Medicare covered services when Medicare is the secondary payer. It is necessary to have the primary insurer's Explanation of Benefits (EOB) and Medicare's Remittance Advice (RA) available when using this calculator. For additional information, please refer to the CMS Internet Only Manual (IOM), Publication 100-05, Medicare Secondary Payer Manual, Chapter 5, Section 40.7.3

This calculator is intended to provide an estimate only, and any special reductions are not included in the calculation.

The calculator will not provide accurate MSP calculations for the following situations:

  • Non-participating providers/suppliers
  • Sequestration
  • 100% Allowed payments (i.e. lab codes)
  • Psychiatric Reduction
  • Tertiary Payments


  BAMT, AAMT and DED can all be
found on the Medicare Remittance Advice
SA, SP and OTAF can all be
found on the Primary Payer EOB
Medicare Remittance
Advice Information
Primary Payer EOB

  BAMT The amount billed by the provider/supplier Enter amount billed by provider/supplier for the service billed. AAMT Medicare's allowed amount Enter the amount Medicare allows for the service billed. DED The amount remaining on the Beneficiary's Medicare deductible Enter amount remaining of the beneficiary's annual Medicare's deductible. Primary
The amount the primary insurance allowed The primary allowed amount is the amount the primary insurance company allowed for the submitted charges. This may also be referred to on an EOB as eligible charges. This amount should equal the OTAF amount. Primary
The amount the primary insurance paid The primary paid amount is the amount the primary insurance company paid for the submitted charges. On an EOB, this may also be referred to as the covered charges. Obligated
to Accept
The amount the provider or supplier is either obligated to accept,
or voluntarily accepts, as full payment, a primary payment that is less than its charges
Obligated to Accept Field (OTAF): There is not a specific column or area on an EOB that indicates the OTAF amount. However, this amount is determined by other information that is listed on the EOB, such as discount, provider write-off, withholding, risk amount, service benefit credit, contractual adjustment, provider agreement, negotiated savings, or an amount that the beneficiary is not liable for. If the beneficiary were not responsible for any of these amounts, then the OTAF amount would be the same as the SA. Using an OTAF amount will indicate that there is a discount that the beneficiary was not responsible for. This may have to be manually calculated, by taking the billed amount minus the discounts to calculate the OTAF.

"Obligated to Accept" is a term used when a supplier has a contractual agreement with the primary insurer to accept the primary insurer's allowed amount as payment in full. When the supplier is obligated to accept, the secondary payment is based solely on the primary insurer's allowed amount.
The amount that Medicare will pay After the calculations are done this is the determined amount that Medicare will pay. Patient
This is the amount billable to the Medicare beneficiary The patient responsibility is the financial responsibility assigned to the beneficiary, for the unpaid portion of the claim, after the coordination of benefits.
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Last Updated Tue, 03 Mar 2020 13:19:20 +0000