Tax vs "up" spells - what's the Ob?

Burning Wheel First Reading
1

When a player casts a spell with a carat in the Ob, what is the final Ob of the tax test? Is it the base listed in the book, or is it the value they bring it up to?

2

The tax obstacle is the the casting obstacle as listed in the book plus any modifications from casting Hastily.

3

Thanks. Is this also the case for BWR? I couldn’t find a page reference when I looked before but I may have overlooked something.

4

I don’t know. Don’t have any BWR books handy.

5

Well, in both cases the Ob is fixed - “up” spells just let you spend margin of success for effect.

6

Thanks for the quick replies folks