Any chance you could share a screenshot so I can help with troubleshooting?  Or if you could provide a link to a base with example data that would be excellent

Hey @Shirley_Kawafuc!

I think that the comma in your 40,000 value could be causing unexpected problems.
Try this:

Thank you so much @Ben_Young1 and @TheTimeSavingCo! Removing the comma fixed the formula. I'd like the "Deduct Formula" column to continue subtracting from my set total of $40,000 budget IF there is a "Total cost" associated with student tickets (see screenshot). By chance do you know to achieve this? Do I need to add a hidden column that holds just the set budget amount? 

Hey @Shirley_Kawafuc, are you looking to get something along the lines of this?

Hi @Ben_Young1 , yes! The only change is: I want the "Remaining Budget" amount to get smaller and smaller as the total costs accrue, instead of each line starting over from $40,000 every time. 

Weirdly, for some reason, my Deduct formula column isn't working now. In screenshot, you'll see the amounts it's giving are incorrect. I have the formula set up like: