Even in tempered music theory, calling a note a sharp or a flat generally depends on the scale. For eg: Bb major uses: Bb C D Eb F G A Bb while A# major uses:

Even in tempered music theory, calling a note a sharp or a flat generally depends on the scale. For eg: Bb major uses: Bb C D Eb F G A Bb while A# major uses: A# B# Cx D# E# Fx Gx A# (x indicates double-sharp) Despite all the notes being exactly the same on a tempered instrument.