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Scientific Method

The Scientific Method calculates an adjustment schedule from the acquisition date to the redemption date, extracting the per period amounts from this schedule. The premium amount is adjusted across the life of the bond using the Yield at Purchase rate. You can use this method only for fixed income securities.

Tamarac Reporting uses this formula for amortized amount per period:

Mortgage-Backed Cost Basis Adjustment Equations

The goal of the cost basis adjustment logic is to ensure that a mortgage-backed security holding's cost basis will be adjusted each period such that at the security's maturity date the holding's cost basis is reduced to zero.

With only the return of principal transactions, the cost basis will not be adjusted periodically down to zero. This is because the return of principal is only adjusting based upon the par value of the security. In order to get the correct draw-down, the initial cost basis (aka “clean price”) of the bond must be used, not the par value. Thus, additional “amortization” values must be calculated and applied to correctly adjust the holding cost basis for each payment period.

Equation: Cost Basis Adjustment

This is the total cost basis adjustment that should be applied within the coupon period.

Equation: Return of Principal

This is the value of the periodic return of principal transaction that is based upon just the par value of the security.

Equation: Additional Adjustment (aka “Amortization”)

The amortization is the difference between what is currently being recorded for the cost basis adjustment via the return of principal transaction and the actual periodic cost basis adjustment. This is the value that Tamarac Reporting is calculating.

Equation: Custodian Cost Basis Adjustment Values

These equations do not exactly match every custodians calculated values for cost basis adjustment:

To learn more about amortization in Tamarac, see Amortization and Accretion Report and Set Up Securities and Accounts for the Amortization and Accretion Report.

To set amortization method for a security category, use Amortization Method.