The City standard is that all fields are mandatory unless they are marked as optional. This is because most fields in a form are mandatory, so it less cluttered if only optional are identified.
The top of the form must have a statement, either:
All fields are required.
All fields are required unless marked (Optional).
The text should be at the top of the page, above the first section of questions. On a multi-step form, the text appears between the stepper and the questions and appears on every step.
Optional fields are marked with the word (optional) after the label, in brackets, with a font of #737373
