Total Pension Periodic Pension Cost = Current Service Cost+Interest Cost-Actual return on Plan assets+/- Actuarial losses/Gains due to changes in assumptions affecting PBO+Prior service cost

I understand that interest cost is calculated on the Beginning fund status using the discount rate.

In the above formula, Can anyone please explain about the how Actual return/Expected return on plan assets is calculated?

Actual return on plan assets is . . . well . . . the actual return on plan assets. They might give you that number, or they might give you the return rate; if the latter, you have to multiply it by plan assets at the beginning of the period.

Expected return is the expected return rate times the plan assets at the beginning of the period. Under IFRS, the expected return rate is the same as the discount rate for the plan liabilities. Under US GAAP, they’ll give you the expected return rate.

Note, by the way, that in your formula where you have “Actual return on Plan assets”, it’s more common to have “Expected return on Plan assets”.