Kapie

PBO at B/S date is PV of benefits that is calculated with latest actuarial assumptions that is certified by your actuaries. Fair value of your pension on B/S date is the figure that your pension benefits investment manger gives you.

PBO - Fair value of pension assets = Net funded status. +ve => net liability; -ve => net asset

This is how USGAAP works, plain and simple that makes economic sense.

IFRS gives some more room for smoothing. The PBO at B/S date is net to-date figure; meaning it includes all unrecognized stuff: actuarial gains/losses, past service costs.

Since you did not recognize some stuff, just get them off of PBO to calculate the funded status:

+ PV of the defined benefit obligation at the balance sheet date [~DBO]
– unrecognized actuarial losses [~DBO is inclusive of this unrecognized loss, adjust]
– unrecognized transition liabilities [~DBO is inclusive of unrecognized liability, adjust]
– unrecognized past service costs [~DBO is inclusive of unrecognized service costs, adjust]

– the fair value of plan assets at the balance sheet date

= Net funded status

IFRS says you can recognize the unrecognized stuff (amortize) slowly to bring them into B/S.