SO header shows No Tax

Hi Team,

I would like to inform you the  followings:

1) I have created a Sale Order .

2) SO- Line is shipped and closed and I can see that Tax has been applied on SO Line .

3) SO Header shows as "Booked" and under Tax filed , the value is  Blank .

   Is it so , that since the SO header is in Booked status , the Tax will not been shown , until and unless the SO header is Closed.

That is, as per the seeded functionality , when the SO header gets closed after the month end ,the tax will be populated on the SO header.

Can anyone please confirm ,