My husband just lost his job while I was on vacation, so I wanted to cut my vacation short to save on money. What's the best way to tell my boss without letting him know the real reason? I don't want him spreading the news throughout the whole company.
In the US, at least, if you're in a salaried position, your vacation days are often 'use them or lose them' and can't be converted into liquid cash. If this is the case, you might be better off using that time to help your husband get back on his feet or think about side-jobs that will help you make up the income gap. If you've travelled someplace far away, it may cost you more just to return home earlier, so you ought to just enjoy the vacation time if you can.
If you're in a position where you get paid per shift, just call him and say that there was a change in plans and you'll be available again on Monday, if there's any work that's available. Say "A personal matter came up" if you feel like you have to give a reason.
If your manager presses further, just say the hotel was terrible or your car broke down on the road - it's none of his business so it really doesn't matter what you tell him.
He might say that there isn't work available if the schedules are planned in advance - if that's the case, there's nothing you can do but take those days off and make the best of it.
Simply let your boss know that you are cutting your vacation short, that you'll be back in the office on such and such a date and that they can take you out to lunch if they feel strongly enough about it.
In general, your personal and your family circumstances are your business and no one else's including your management. Personally, I'd say to anyone who asks "My plans for a long, relaxing vacation fell through" - which is totally true, by the way - and I'd add with a tight smile "Any other questions?"