The main challenge does not stem from the mathematical formula but from the cash flows to be considered for EIR calculations:

  • Systems for retail business do not have cash flows.
  • Systems lose historical cash flows (real cash flows).
  • Systems cannot calculate future floating cash flows.
  • Systems cannot distinguish between EIR relevant and irrelevant cash flows.
  • Systems cannot consider prepayment behaviour (only contractual cash flows).
  • Systems cannot handle complex fixing agreements.

The solution has to calculate the amortisation plan over the complete lifecycle of a deal and to provide separate amounts for all relevant cash flows, including

  • premiums, discounts and upfront payments
  • transaction costs
  • forward adjustments
  • costs of embedded separated from the host contract
  • hedge adjustments at the termination of a hedge relationship
  • initial basis adjustments for late hedges
  • unwinding of the impairment adjustment

A further challenge is to know when the EIR has to be recalculated:

  • No recalculation of EIR in the following cases:
    • Not because of unexpected capital changes such as partial notional redemptions!
    • Not because of an impairment!
  • EIR has to be recalculated in the following cases:
    • For floating-rate products at the new fixing date.
    • For credit lines at each drawing.
    • For security long positions at each buying transaction.
    • After a contractual change or new estimation of the repayment plan.
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