Comingling is. In this case there is a clearly articulable reason why ("our bank is going out of business"), and it's temporary, documented, etc. The twin risks to avoid are appearance of embezzlement, and appearance that you're treating the business account and personal account as one (which potentially allows piercing corporate veil/attaching personal assets), but if your building is on fire, you're allowed to break the window to rescue the kitten.

It's an "antipattern" (and usually a strong sign that something is badly wrong) but it's not illegal... "sinful" is a useful hint that something is "norm" related.

Yeah, I didn’t say illegal. Often “cardinal sin” is just a playful way of saying “something thou shalt never do.”

Also nal and naa but no: it's "comingling" that's bad. If you explicitly document the transactions, don't do it all the time, and ideally use matching amounts in and out, it's not comingling.

Interesting that its viewed so critically in the US.

If documented its no problem and not uncommon at all in Germany.

In fact many business owners pay something like credit card bills personally and reimburse through the company later.

That is far more common in the US (basically paying expenses on your personal cards, expensing to the company after the fact). You can also advance on some expenses sometimes (this can be abused so there are some accounting restrictions on how you'd do it, etc.).

What is weird/scary (especially when not documented clearly and in advance) is moving your entire bank balance into a personal account. Aside from government/tax/legal, you'd have your investors (in a venture/angel backed company) to justify it to. It's justifiable in this truly exceptional case of SVB imploding and no other bank account being available. (It gets harder to justify in a larger company with lots of investors and more money involved; moving a $100mm balance in a company where you were down to 10% ownership to a personal account even in this situation would be weird AF and depending on the banks involved might cause you problems. I probably still would have emailed counsel and investors/etc. on thursday morning to ask what to do; likely would have sent it to lawyers to handle actually in the huge-account situation.)

I see. That makes sense. Thank you for clarifying.

Also, imagine the case where you do this and you're wrong. You panic but you're in the minority and there's no bank run and a week or two goes by and the bank is still fine.

Now you've got a weird thing to explain and no vindication.

Philosophical problem of "justified true belief"/Gettier problem. (https://en.wikipedia.org/wiki/Gettier_problem -- I learned about this from one of the Rap Genius founders when I was back in YC, lol.)

Generally the law handles this through the "reasonable man" standard; i.e. "would a reasonable man, knowing what you did at the time, have done what you did?" This would allow you to shoot someone in self-defense who was holding a realistic looking toy gun at a child (which you believed to be a real gun, unlawful intent, etc. at the time).

Wouldn't this be other way around. First pay yourself and then spend that money on company bills? Which sounds very iffy to me as European.

Not if it’s documented, short-term and for a very extraordinary reason.