12 C.F.R. § 628.36
(2) This section applies to exposures for which:
(b) Rules of recognition.
(2) A System institution may only recognize the credit risk mitigation benefits of an eligible credit derivative to hedge an exposure that is different from the credit derivative's reference exposure used for determining the derivative's cash settlement value, deliverable obligation, or occurrence of a credit event if:
(2) Partial coverage. If an eligible guarantee or eligible credit derivative meets the conditions in §§ 628.36(a) and 628.37(b) and the protection amount (P) of the guarantee or credit derivative is less than the exposure amount of the hedged exposure, the System institution must treat the hedged exposure as two separate exposures (protected and unprotected) in order to recognize the credit risk mitigation benefit of the guarantee or credit derivative.
(5) When a maturity mismatch exists, the System institution must apply the following adjustment to reduce the effective notional amount of the credit risk mitigant:
Pm = E x [(t−0.25)/(T−0.25)]
Where: Pm = effective notional amount of the credit risk mitigant, adjusted for maturity mismatch; E = effective notional amount of the credit risk mitigant; t = the lesser of T or the residual maturity of the credit risk mitigant, expressed in years; and T = the lesser of 5 or the residual maturity of the hedged exposure, expressed in years.
(e) Adjustment for credit derivatives without restructuring as a credit event. If a System institution recognizes an eligible credit derivative that does not include as a credit event a restructuring of the hedged exposure involving forgiveness or postponement of principal, interest, or fees that results in a credit loss event (that is, a charge-off, specific provision, or other similar debit to the profit and loss account), the System institution must apply the following adjustment to reduce the effective notional amount of the credit derivative:
Pr = Pm x 0.60
Where: Pr = effective notional amount of the credit risk mitigant, adjusted for lack of restructuring event (and maturity mismatch, if applicable); and Pm = effective notional amount of the credit risk mitigant (adjusted for maturity mismatch, if applicable).
(f) Currency mismatch adjustment.
(1) If a System institution recognizes an eligible guarantee or eligible credit derivative that is denominated in a currency different from that in which the hedged exposure is denominated, the System institution must apply the following formula to the effective notional amount of the guarantee or credit derivative:
Pc = Pr x (1-Hfx)
Where: Pc = effective notional amount of the credit risk mitigant, adjusted for currency mismatch (and maturity mismatch and lack of restructuring event, if applicable); Pr = effective notional amount of the credit risk mitigant (adjusted for maturity mismatch and lack of restructuring event, if applicable); and Hfx = haircut appropriate for the currency mismatch between the credit risk mitigant and the hedged exposure.
(3) A System institution must adjust Hfx calculated in paragraph (f)(2) of this section upward if the System institution revalues the guarantee or credit derivative less frequently than once every 10 business days using the following square root of time formula:

Where TM equals the greater of 10 or the number of days between revaluation.