Equations aren't working once I email the Fillable PDF to someone

I am putting together a clothing order form for our employees. They have three clothing options to choose from. Each clothing line has a description of the item, base price, blank box for size, blank box for the QTY they want and then a total. At the end of the forum is a subtotal, add tax (6% Idaho sales tax) and final total boxes.

Total=baseprice*QTY

Subtotal=Total boxes added together

Salestax=Subtotal*.06

Finaltotal=Subtotal+Salestax

On Adobe Acrobat all my simple equations work but once I email it, the equations stop working and the boxes just show zeros. I really need these equations to work so employees know exactly what they owe when they submit their order.