Massallah pertanong to Zakaah

Hazrat Mufti Saheb
Bismi Ta’ala
I am a shareholder of a firm of professionals rendering sevices with a 5% holding. For zakaah purposes:
our balance sheet shows time spent by our staff as an asset that is then charged to our clients – is this considered as stock in trade (thus zakaatable) or must it be excluded for zakaat?