If a company's name is Daniel's what is the correct possessive form ? Like in the sentence " I used to work at Daniel's ' / 's Human Resources Department "
When used as the name of a company,
Daniel's has an implicit subject attached to the possessive Daniel -
Daniel's Motor Repairs, and the like. Maintaining the unspoken subject would mean
Daniel's Stores' HR Department is expressed as
Daniel's HR Department.
Practically all native speakers would not consider this and simply say
Daniel's HR Department for simplicity's sake.