The term 'BILL ADD-ONS' refers to additional charges that may be added to a customer's bill. The crossword solutions for this term are TIPS (4 letters), RIDERS (6 letters), and PORK (4 letters). TIPS stands for 'To Insure Prompt Service' and is an optional gratuity given to service providers such as waiters, taxi drivers, and hairdressers. RIDERS are amendments or additions to a bill that are not part of the original agreement. Finally, PORK is a slang term for spending on projects that are not necessary or beneficial to the public.