A trademark doesn’t turn your business into an LLC or S‑corp, you stay a sole proprietor unless you officially register otherwise. That “Notice of Assessment” isn’t an income‑tax form; it’s just the trademark office reminding you they didn’t get the 2024 fee and telling you what’s owed. You pay that fee directly to them, not on your personal return. If your son isn’t using the mark and doesn’t plan to, just let the registration lapse or file to cancel it so no more fees pop up.