You're likely to need a planning permit because of:
Change of use and parking
Using the property for a type of business that differed from how it was most recently used. For instance using a shop front that previously operated as a butcher for use as an office.
Alternatively using the property in a way that may have impacts beyond the property boundaries. For instance not being able to cater for all parking demand on site.
Selling and serving alcohol.
Fixed signage on awnings, walls or even free standing signs.
Including extensions, new structures and changes to facades all need permits.
Business location plays an important part as heritage considerations will mean painting a wall will require a permit.