Some cities and municipal districts require taxpayers (both business and personal) to file a city tax return. Usually these are some % of income, a flat tax on anything you earn inside of their jurisdiction.
Halon does not do these returns as part of your core package, they require an add on.
Some cities that require this add on are:
New York City
Most cities and villages in OH
District of Columbia
Some cities in PA
Your Halon Private Client Pod Manager will explain if you are subject to any of these and will add to your package. This is not available in the Halon Tax service.