Either IRS Publication 525 or 529 contain the following info (also re-purposed from the us gambling law site posted in this thread):
Your sportsbetting records in examination:
<!-- ======================================================= --><!-- Created by AbiWord, a free, Open Source wordprocessor. --><!-- For more information visit
http://www.abisource.com. --><!-- ======================================================= -->
An accurate diary or similar record regularly maintained by the taxpayer, supplemented by verifiable documentation usually is acceptable evidence for substantiation of gambling winnings and gambling losses. In general, the diary should contain at least the following information:
1. Date and type of specific wager or gambling activity;
2. Name of gambling establishment;
3. Address or location of gambling establishment; and
4. Name(s) of other person(s) present with you at gambling establishment.
5. Amount(s) of gambling winnings or gambling losses.
Obviously the IRS list above is not aimed at online sportsbetting. Regardless, the above info can be used as a template. My gambling "diary" (as the IRS publication refers to it) contains:
1. Date and type of specific wager or gambling activity;
2. Name of book
3. Address or location of the book (defined once in the diary); and
4. Amount(s) of gambling winnings or gambling losses.
Of course it's not necessary to list the names of other persons present when I made the online wagers. To do so would be ridiculous, no? Some people may have very unusual cirucmstances, however.
It doesn't seems necessary to list the address or location of the book more than once in the diary. I made list of the books and the addresses and attached it the main part of the diary.
I have listed the name of each book on a per-wager basis. I suppose if a bettor only used one or two books and often had days wherein he made all bets with the same book, it'd be acceptable to list the name of the book with a note that all wagers on that day where with that particular book.
Now so far it seems pretty straghtforward, but number one (1.) on the list leaves a bit to interpretation, as does number four (4.):
1. Date and type of specific wager or gambling activity;
Obviously they want the date, but..
The phrase "type of specific wager" though seems unclear as to how much detail the want exactly. A type of specific wager may be so general as "NFL Wager"; certainly defines the "type" of wager. No where does it say that the specific wager(s) itself must be listed, only the type. So it seems I do not have to list specific teams, the line, or anything else, just the "type" of the "specific wager". The part that muddies this is the word "specific". The publication just as easily could have left that word out, if the IRS didn't want more. Any input on this one?
The other unclear one is four (4.)
4. Amount(s) of gambling winnings or gambling losses.
Ought the amount of winnings or losses be listed per specific wager outcome or may they be netted per session. And while we're on the subject it seems ambiguous as to what exactly constitutes a "session". For online sportsbetting it seems that a session may be considered to be a maximum of one day (unless you regularly go on multiple-day online binges without sleeping -- any manic or crystal meth user online sports bettors out there, lol?).
I go through the effort to closely examine the IRS' guide for a gambling diary because I want it to be accurate and acceptable, yet minimalistic.
If you look at the publications you'll notice that at the end of the description there is a warning that the above list is not carved in stone and, depending on the situation of the audit and the person is question, the requirements may be adjusted. It seems it was purposefully left open to interpretation. Wording it that way serves the IRS while maintaining the burden of proof on the bettor. A case of the ol' 'guilty until proven innocent'. Whatever diary and records you have to show the IRS auditor better be enough for he/she to consider it legitimate. Cover Your Ass!
Related info:
Comprehensive list of IRS Publications (Suggested Reading is Pub.525 and Pub.529): http://www.wwwebtax.com/irs/irs_publications_list.htm
Verifiable Documents (the rest of this post is copied from the above site):
<!-- ======================================================= --><!-- Created by AbiWord, a free, Open Source wordprocessor. --><!-- For more information visit
http://www.abisource.com. --><!-- ======================================================= -->
"includes, but is not limited to, gambling tickets, canceled checks, credit records, bank withdrawals, and statements of actual gambling winnings or payment slips provided by the gambling establishment. When possible, the diary and available documentation of the placement and settlement of a wager should be supported by such documentation as hotel bills, airline tickets, gasoline credit cards, or affidavits or testimony from responsible gambling officials regarding the wagering activity. (Much of this doesn't pertain to online sportsbetting; refer to the suggested IRS Publications, see below)
For information on deducting gambling losses, refer to Tax Topic 419, Gambling Income and Expenses. Refer to IRS Publication 529, Miscellaneous Deductions for information on record keeping. For additional information, refer to IRS Publication 525, Taxable and Nontaxable Income. Also see IRS Publication 17, Your Federal Income Tax. Please read this IMPORTANT Editor's Note regarding navigating IRS publications with Adobe Acrobat Reader. IRS publications can also be ordered by calling 1-800-829-3676."