What's missing here?

IFTA tax isn't based on miles, it is based on gallons burned per mile. The info required is miles ran and gallons purchased in each state. Thus we can arrive at our average miles per gallon (MPG) which will vary slightly each period. You need to know how many miles you ran in each state to calculate how many gallons burned by using your MPG figure.

So drive slow and have a high MPG to pay less IFTA tax.

 

I'm not sure about other states, but Illinois' policy states that you must maintain a mileage log or trip report, as they call it that includes state line crossings, primary routes, etc.. If you fail to maintain these trip reports, then the auditor will use all available documents (bills of lading and fuel receipts) AND PC Miler to establish the miles you have run. What I have decided to do is not bother with keeping trip reports at all. I use PC Miler and enter in all zip codes of every stop (including fuel stops... this is very important). If I take a route that I know PC Miler would not use, I'll pull a zip code or two off my GPS at a couple of points along the way so I can keep PC Miler following me. At the end of each quarter, I run the route through PC Miler using the "Practical" setting. I run a "Fuel Detail" report on TCH's website (I ALWAYS use my TCH account to buy fuel), which tally's up the gallons purchased in each state for me, and plug the miles and gallons into an Excel spreadsheet I've made to do all the calculations. The hardest part of the whole process is copying the data onto the IFTA form -- and I guilt my wife into doing that for me ;-). If I get audited, the auditor will use the exact same process to audit me that I have used to calculate my miles. His or her result should pretty much be identical to mine. I think you can be off by as much as 15% without a penalty, so I know I'm good. It saves a ton of time and headache.

And BTW, I ALWAYS get an IFTA refund… not because of how I do my calculations, but because of how I buy my fuel. I LOVE getting a check from a big government program… almost makes me feel like I should be an Obama supporter… a l mo s t.