A lot of people worry that their ex-partner will try to hide money during a divorce. Years ago, when parties had to rely on litigation to settle their differences, this could be a huge problem. The court system still operates like the 1950s but with email. So a partner who wants to hide assets can just file a paper with the court listing incomplete assets. No one can tell the difference unless they can get the original paperwork. Lawyers also tend to play games with the paperwork. Lawyers make excuses, hide the ball, and otherwise drag out the process where each partner shares assets with each other. For most people, they'll spend more on legal fees hiding the money than they would if they had to share the community property that they are hiding.
All of this changed, however, with the advent of the internet and uncontested divorces. It is really hard to hide a bank account when all your bank records are online and searchable. You can't really conceal a retirement account balance when it's online, and your employer has the records. The IRS even keeps online records of everyone's most recent tax filings, and these are available for free to the other spouse.
People who try to delay sharing records, or hide records altogether, pretty quickly run into problems. Can someone still hide cash? Yes, but if they're driving a car and living in a house, their transactions are still going to be online in the form of mortgage records, car payments, and so on.
For most people, record sharing is easy and quick in an uncontested divorce. This frees up time for problem solving with the goal of making both partners comfortable. Divorce used to be a financial shock. But now there are ways to minimize any issues, when couples work together.
Here is a link to the Family Law Handbook for Washington. Check out page 10 for a longer explanation of community property.