How to keep a gambling diary for tax purposes

Last update: February 24, 2026

What it is and why you need one

A gambling diary is a record of your wins and losses. For example:

Sample Diary of Sessions
Date	Wins	Losses	Where	Game	Who With
May 5	$250		Park MGM	BJ	-
May 5		-$200	NY NY	slots	husband
May 6	$200		Stratosphere	slots	husband
May 6		-$300	Stratosphere	BJ	Spanky McBluejay
Total	$450	-$500	All of the above on the Las Vegas, NV strip

You need a diary because the IRS says you have to have one, and because if you get audited without and don’t have a diary, expect to pay more taxes.

Publication 529 says:

Diary of winnings and losses. You must keep an accurate diary or similar record of your losses and winnings. Your diary should contain at least the following information.

The date and type of your specific wager or wagering activity.
The name and address or location of the gambling establishment.
The names of other persons present with you at the gambling establishment.
The amount(s) you won or lost.

Pub. 529 got that from IRS Revenue Procedure 77-29, which explains how the diary is your primary evidence:

An accurate diary or similar record regularly maintained by the taxpayer, supplemented by verifiable documentation will usually be acceptable evidence for substantiation of wagering winnings and losses.

We’ll cover that “verifiable documentation" later.

The IRS calls the records a “diary”, but what they describe is a “journal” or a “log”, so I’ll call it a log from here on out.

What do you do with it?

You use your log to figure how much gambling income and losses to report. Contrary to popular belief, the total of your W2-Gs is not your gambling income. I have a whole article explaining how to report, but in short: your wins are the total of all winning sessions, and your losses are the total of all losing sessions. You do not net the difference, wins and losses must be separate.

Even if you think you’re supposed to report the W2-G total as your income, that doesn’t absolve you from keeping the log; you’re supposed to keep it no matter how you figure your wins and losses.

The other reason to keep the log is in case you get audited. You need to be able to show that you didn’t win more than you claimed, and you have to substantiate any losses you had.

What constitutes a “session”?

The IRS doesn’t explicitly define what a “session” is, but a reasonable definition is: Play at one game at one casino, not spanning more than one day. (source) In other words:

Changing games ⮕ new session
Changing casinos ⮕ new session
New day ⮕ new session

Looser than that will probably not fly. Some gamblers have suggested creative ways of defining “session”. Unfortunately for them, the IRS (and the courts) generally don’t like “creative”. These creative session ideas are either explicitly disallowed or else very unlikely to be accepted.

BAD IDEA: Treat the whole year as one big session. Get real. The IRS would never accept this even if it weren’t specifically disallowed, and it is specifically disallowed, by Shollenberger v. Commissioner. (source) Also IRS Notice 2015-21 proposed to codify that a session should never span more than a calendar day. That proposal was never officially finalized, but since we know the IRS thinking on this matter, that's how you can expect them to treat it if you have a dispute.
BAD IDEA: Treat all play at a particular casino during the year as a single session. As accountant Russ Fox says, “this fails the smell test”. (source)

On the other hand, don’t be too conservative: keep your sessions as long as the guidelines above allow. That is, don’t start a new session just because you pause for any reason (e.g. meal / sleep / show), as long as you return to the same game at the same casino on the same day. That’s because the longer the session, the less chance you’ll wind up with taxable income. Let’s say you played in the morning and won $500, then played in the evening and lost $500, as a single session your result would be $0. But if you treated them as separate sessions, you’d have a $500 win and a $500 loss. You can’t deduct the $500 loss unless you itemize (and you probably aren’t), so now you get to pay taxes on $500 of income. Also, you’ve inflated your AGI which comes with its own problems.

Making sure your log passes muster

Obviously, anyone can write any number down in a log, and the IRS is aware of that. Keeping backup evidence can go a long way to validating your log.

To prove you went to the casino in the first place, save airline boarding passes, gas receipts, and hotel receipts. Take time-stamped pictures in the casino.
To prove you won or lost as much as you claim, deposit or withdraw your gambling budget from a bank account. Don’t keep it around as cash.
Consider having a separate bank account just for gambling. Your bank will probably let you open an extra Savings account at no cost.

The IRS encourages backup evidence specifically. But some of their suggestions veer into the absurd, such as recording the number of the slot machine or table game you play. What if you can’t find the slot machine number? “If not displayed on the machine, the number may be requested from the casino operator.” Only the IRS, man. (Revenue Procedure 77-99)

Note that if you get audited, the IRS will have easy access to records at any regulated online casino. (IRS, Atty. S. Turanchik) That can be a benefit, because the online casino tracks deposits and withdrawals, which can help you prove win and losses.

Consequences of not keeping a log at all

If you don’t keep a log you could wind up owing lots more in taxes. Here are cases in which taxpayers didn’t maintain a log and paid the price.

Bill Remos won $50k in a blackjack session, and had at least $50k in losses for the year, so he shouldn’t have owed any taxes, but he didn’t keep a log. The IRS made him pay the taxes on his $50k win without letting him deduct any losses to offset his winnings. Ouch.
Donald Mock claimed gambling losses of $31,974. He didn’t keep a log. The court disallowed all his losses.
The Szkircsaks claimed losses of $15,645. They had some records but not a proper session log. The court denied nearly $10,000 of their loss deduction, allowing them to deduct only $5,840.
(sources for cases)

Maybe you’ll get lucky without a log and not have to pay any extra tax, like Francis Gagliardi did, by presenting other evidence. First, don’t hold your breath, that case is definitely the exception and not the rule. Second, his “win” was bittersweet. As one CPA put it, “Mr. Gagliardi had to go to Tax Court, hire two attorneys, have expert testimony, [how much did all that cost?] and then he won his case. Had he kept a gambling log it’s likely he wouldn’t have needed to go through the effort.” (Russ Fox, CPA)

The log must be contemporaneous

The journal must be contemporaneous, meaning recorded as it happens. You can't wait until the end of the year and then try to piece it all together.

It’s unclear whether you have the burden of proof to prove that your journal was contemporaneous, or if the IRS has the burden of proof to prove that it wasn't. For example, if you record everything in the notepad app on your phone, there’s no automatic timestamp for each entry, and usually not even a creation date listed for the note file. On the other hand, for years the IRS accepted hand-written diary entries which have no machine-generated timestamp, so if they'd accept that, then why wouldn't they accept a phone notepad?

I don’t have good answers to these questions. I've never heard of the IRS rejecting a journal because it didn't look contemporaneous, but there might be cases I don't know about. So, here’s my feeling about how to handle things:

Personally, I just use the notepad app on my phone. But these days I generally have no more than $1000 in wins or losses. If I won considerably more, I might consider using machine-generated timestamps.
If you want a machine-generated timestamp for a phone-based notepad, email the contents of the note to yourself each day.
Take a photo of each log entry with the casino game in the background. Use the timestamp feature if your phone has one.
If the IRS rejects your contemporaneous journal as not being contemporaneous, remember that you can appeal. I’ve read lots of tax cases, and taxpayers often have success in court, especially when an auditor is being unreasonable.

Can you use win/loss statements instead of a log?

No. You can use win/loss statements that casinos provide at the end of the year as backup evidence to supplement your diary, but not as your main evidence. As one tax attorney says, “The IRS has consistently and regularly rejected the use and reliance upon such information. The primary reason for the IRS belligerence is simply because the casinos explicitly state in their reports that the reports are inherently inaccurate and should not be used for accounting purposes.” (Reece B. Morrel Jr., CPA)

Even if you could, you wouldn’t want to, because they overstate your income. If you play slots for five hours you might play 4000 spins and have a net loss, which is what you’d record in your log. But win/loss statements typically count each individual spin, so over your 4000 spins you might have had around 400 winning spins, and those will show up on your statement as wins (taxable), even though you didn’t really win.

Now multiply that tragedy by the whole year. You know you won only $100 for the year, but on a win/loss statement that tracks every spin, that could look like $10,000 in wins and $9,900 in losses. If you’re not itemizing (and you probably aren’t), then you get to pay taxes on nearly $10,000 of phantom income. That phantom income will also increase your AGI, fact which comes with its own problems.

If you thought session logs were bad…

For decades the IRS ostensibly expected gamblers to track every individual bet. That means every pull at a slot machine, every individual round of blackjack, etc. Yeah.

They didn’t say this explicitly, but they implied it, because they didn’t offer an alternative. They were adamant that gamblers had to count all wins and losses, but were mum about how gamblers were supposed to do so.

So gamblers had no idea what to do. As one CPA put it, “Between 1934 and 1977, it was anybody’s guess as to the record keeping requirements for wagering…” (Morrel Jr., CPA)

In 1977 the IRS finally gave some guidance: It said gamblers should keep a log (or “diary”, in their parlance) of gambling actiity, including date, type, location, and amount won or lost. (And for some reason, the names of anyone else present.) (Revenue Procedure 77-29)

But the IRS was still stingy about what exactly constituted a win and a loss. Then came the case of Shollenberger v. Commissioner in 2008 which enshrined the concept of session reporting. That finally gave taxpayers guidance about exactly what they were supposed to do. Even so, occasionally a clueless IRS auditor will insist that a gambler “pay taxes on every winning pull at the slot machine.” Fortunately that absurdity gets overturned when it goes to court., but it shouldn't have to come to that. (Park, et al. v. Commissioner of IRS, No. 12-1058 • D.C. Cir. 2013) Commenting on another case, one CPA said, “Most of te personnel within the IRS don’t have experience with gambling, and even an IRS attorney [in this case] had trouble explaining an IRS-suggested procedure on gambling (a gambling log). (Russ Fox, CPA)