Ever since our first holiday, we've had "joint" monies. At first it was a third wallet/purse which we used to buy meals, attraction entries, etc - basically anything we did together that was roughly equal cost. We used our own wallets/purses for "unequal" things like souvenirs etc. When dating and going out for meals, etc., we'd always go halves.
So when we got married and bought a house, it was virtually automatic, that everything we equally benefitted from was paid from joint monies, so we set up a joint bank account, got joint credit cards, etc. That gave full transparency as to what was going out of the account for all household costs, cars, childcare, presents, food, clothes, etc. etc.
We each have our own personal accounts and personal credit cards, so we also have our "own" money, but it's minimal, just for occasional/gifts for eachother, etc., As our wages went in, the majority was transferred to the joint account.
All that's worked well for our 30 years of marriage. No secrets at all, we both have access to each other's finances, simply because all bank statements, payslips, bills, etc are kept in a big lever arch file, so we can see how much each other was earning, etc.
Right from early dating, I made it clear that honesty and transparency with money was a deal-breaker, and by setting the scene so early on, we've had no problems. Start as you mean to go on and you have less chance of being screwed over later!