This very same topic was discussed at length on the "FAQ for Newbies" board.
Click on that board, go to the last page of that board (around pg.171) and look for the heading "Financial subterfuge for married men".  That thread was dated 7/8/2002 and was started by gspider.

Easy...don't have an SO

When my first marriage was heading south, a simple expedient restored it to its rightful place:  separate bank accounts.  Of course there has to be sharing and accountability and my rule was my wife could look at my financial records any time she wanted.  The marriage eventually dissolved, but for other reasons.
In my second marriage, we had separate bank accounts from the beginning, and it's been smoother although not without its rough patches, but that's part of the human condition.

Money Management 101

Take up an expensive guy hobby like golf. But don't actually do it.

Another absolutely fool proof way to launder funds and gain private time is simple.  Buy a BOAT!

Then when you want to hobby you just tell your wife the engine needed some expensive thing and she will never question it.

Of course the downside of this idea is then you might find yourself spending your hobby time and money, trying to keep the damm boat from sinking...

Ok, so I'm a hooker not an accountant, what do I know...

Giggle,
TS Jamie

Re: Money Management

Always cash your checks whether they be wages or expense reimbursements.  Buy everything on credit....it helps if you have a bank account that is NOT shared....use convenience checks from the credit card companies or draw money from an ATM with  cc instead of your regular bank card.....pay for dinner or lunch with your colleagues and get cash reimbursemnt.....offer to your SO to fund brokerage accounts electronically and  have her give you cash.....same thing with kids contrib to 529 plan, take cash and fund the money electronically....if you are a salesmen (which I am) you can travel via automobile and get expense reimbursement from your company and just cash those checks.....too bad for you your SO handles the finances, hard to hide things.....

My SO handles our finances also and I can't see any way I could manage it without a couple of cash only enterprises which the she doesn't know about.

I take those expense checks and stash them until I need them.  Also put a little $ away from each ATM withdrawl.

Cash is a way of life in LV, so I always carry some.  It's not uncommon to lose a couple hundred at the tables, and I make certain to mention all my losses at home.  On winning nights, I mention the win, but scrape a little off the story.  Thankfully, I get to the casinos 2-3 nights a week, so that's plenty of opportunity to slice a little off the top.  I play frequently (but small amounts), so it's like a 2nd job.  Otherwise, I'd lose all the hobby money, and that would be BAAAAAD.