I am planning to buy a gas station. Do I have to file form 720. Is there a requirement for me to collect and dispense excise taxes as a retailer of gas.
In most situations, the gasoline retailer pays excise taxes to the wholesale supplier and it is the wholesaler that is required to submit form 720.
Gasoline retailers are not included in the definitions or those required to file in the instructions for Form 720. See the instructions at http://www.irs.gov/instructions/i720/ch01.html#d0e107
If you only have retail sales is not usually required to do any reporting or to submit form 720.
There are sites and publications with extensive tax information of gasoline retailers.
From page 50 http://www.unclefed.com/SurviveIRS/MSSP/gasretaileratg-12-16.pdf
"A Retailer generally is liable for the federal tax on gasoline, diesel fuel, or kerosene only when the operator blends taxed fuel with previously untaxed fuel or when the operator delivers dyed diesel fuel or dyed kerosene into the fuel supply tank of a registered diesel fuel powered highway vehicle. See previous discussion on blending.
A Retailer generally is liable for tax when it delivers propane and other liquefied petroleum gasoline (LPG) into the fuel supply tank of a registered highway vehicle. As of October 1, 1997, the tax rate on propane is $0.136 per gallon."
Please ask if you need more discussion or clarification.