Similarly, if a landlord confiscates your possessions without legal cause, that is criminal theft; but if you walk away owing rent, that is a civil matter that has to be prosecuted at the landlord's expense.

To expand on this just a bit. Theft occurs when the thief has no right of possession. An employee stealing pencils has no prior claim on the pencils. They may be provided as a courtesy to complete the employee's work, but they do not belong to (are not possessed by) the employee. On the flip side, the money owed to an employee is the the property of the employer until the employer relinquishes that claim. Thus, the "crime" isn't that the employer took what it doesn't have a right to possess, but that it failed in its obligation to the employee by contract.

Failing to pay wages is already criminal in various jurisdictions. For example, in California, it's been a misdemeanor, since 1937, to fail to pay wages within the predefined schedule (schedule can set by employer within strict limits), and separately a misdemeanor to "Having the ability to pay, willfully refuses to pay wages due and payable after demand has been made." See CA LAB § 215, CA LAB § 216, etc.

If the bank transfers money out of my account without my permission, is that theft or breach of contract? After all, money in my account is just the bank owing me money, it's not actually my money?

So for clarification, if some property of the employee is stolen that would still go to a criminal court? Say, the company has a bring-your-own-device policy, employee brings their personal laptop, leaves it in the locked office over lunch break, laptop is stolen. This would be theft and not breach of contract and therefore go to a criminal court?

Or if I rent a car and don't return it, is it theft or breach of contract? How is "I borrow your car and don't return it --> theft" different from "I borrow your money and don't return it --> breach of contract"? If I borrow money and keep it with no intention to return it, is it theft or breach of contract? Does it make a difference whether I deposit cash in the bank (I possessed it first) or if my employer deposits it (I never possessed the cash)?

gerrit, I read about the "not returning a rental car" by coincidence, and in California it seems the rental company (and police) can assume it is theft if you don't return the car within one week from the contract ending. Not quite the same as "it is theft", if you have a good excuse, like spending two weeks unconscious in hospital, then it isn't theft.

The difference between the car and the money is that when you borrow a car you agree to give the same car back. Disposing of that car in some other way permanently deprives the owner of it. When you borrow cash you generally don't agree to give back the same individual notes or coins. You can make good your debt with any reasonable set of coins or notes that sum to the right amount.

@gerrit when you deposit money in the bank you are lending it to them to do with what they wish. Your contact with them will allow them to deduct fees and anything else they say you owe them. Didn’t you read the terms of your deposit account?

Is it a crime if the employee is spending time on stack exchange during work hour (basically you steal your working time which belongs to your boss)?

@lalala No, because you cannot steal time.it is a breach of contract.

@quarague Correct. The laptop was owned by the employee, then someone else took unlawful possession of it. That would indeed be theft (if not also breaking and entering).

@DaleM so you're saying unauthorized transfers by your bank (gerrit's question) is then a breach of contract? I suppose it may be to the individual depositor but pretty sure it's a violation of the banking license and would be considered a crime by the state.

@lalala It may be. See 18 USC 1346 which explicitly makes this kind of thing criminal fraud because of 18 USC 1341. You have permanently deprived your employer of their right to the services you should have provided. It would, however, require you to expect to achieve some gain by doing so, and ego boosts probably don't count. Also, Federal courts have not been super happy with expansive readings of this clause, particularly when they end court a bit early on Friday so they don't miss their golf tee time. Did they permanently deprive the public of an hour or two of their honest services?

@Chan-HoSuh In the US, electronic funds transfers are under 15 USC § 1693, and/or more restrictive state laws/fed regulations. Once reported to the financial institution, unauthorized transfers are required to be investigated and resolved per 15 USC § 1693f. Any failure to comply with 15 USC § 1693, including by the financial institution, is a crime, per 15 USC § 1693a(2), and caries civil liability, per multiple sections of 15 USC § 1693.

@gerrit Re: bank unauthorized withdrawal of money via EFT: (In US:) What the actual removal is will depend on what exactly happened. Once reported to the financial institution, unauthorized transfers are required to be investigated and resolved per 15 USC § 1693f. With some limitations, if the financial institution doesn't resolve it in 10 business days, they are required to provisionally credit the account with the full amount (15 USC § 1693c) and then have a total of 45 days to fully resolve the issue. Violations of that are criminal (see above).

@DaleM As to your “toss-up“ between theft or murder being the first crime: the concept of the value of human life has existed since the dawn of humanity while the concept of property and property rights was developed at some later point along with that of human civilisation.

@DavidFoerster tell that to Tharg when Og killed him for taking Og’s piece of mammoth