under IFRS it is reported as net interest (cost) expense. because they required expected return and interest expense to be equal, both can be simply netted under the line “net interest expense.” Gaap allows differences hence expected return and interest cost are split.
Plan assets x Expected return is the return on plan assets not interest expense. Interest expense under GAAP and IFRS is measured the same way: Begging PBO x discount rate. However, under IFRS the discount rate is the same as the expected return and therefore you can calculate the NET interest expense (interest expense - expected return on plan assets) as: funded status x discount rate.
Also, be careful when you are choosing between actual and expected return. Expected return is used to calculate pension expense and actual return is used to calculate fair value of plan assets.
My initial response might have been a little confusing, so let me rephrase it:
That is not the computation of interest expense; it’s the computation of return on plan assets.
Under US GAAP:
Interest expense = beginning value of PBO × discount rate.
Interest expense is the adjustment to the PV of the pension liability from amortizing the discount; it’s simply a matter of time and the discount rate. It has nothing – nothing! – to do with plan assets. It increases the pension expense on the income statement.
Expected return on plan assets is an actuarially smoothed version of the actual return on plan assets:
Return on assets = beginning value of plan assets × expected return.
The actual return increases (we hope!) the value of the plan assets and the expected return reduces the pension expense on the income statement. Both of these have nothing – nothing! – to do with plan liabilities.
Under IFRS, the discount rate for pension liabilities and the expected return on plan assets have to be the same rate (they can be different under US GAAP), so IFRS nets the two: