The City of Sunnyvale requires a permit if a bathroom remodel includes any of the following:
replacement of the tub/shower enclosure,
relocation of plumbing fixtures or cabinets
installation of additional plumbing fixtures
A permit is NOT required for replacement of plumbing fixtures (sink or toilet) in the SAME location.
If a permit is required, it shall be obtained prior to the start of the remodel.For more information, click on the hyperlink here --> Sunnyvale Residential Bathroom Remodel Building Permit Requirements