I also have gotten several inquiries like this one My credit card company is asking for my current income citing "Federal Regulations" which started me wondering just what is considered 'income'.
I do realize my circumstances aren't exactly the norm, as I haven't had significant W2 income for a decade or more. I do part-time contracting/consulting work, and in an average year might net $25-30K or so. (I spend maybe $20K, so that's fine.) I have investments that (again on average) appreciate rather more than that, but since they're not actively traded, and a lot of them are in IRAs, that growth never appears on tax forms. So what does the credit card company consider my income to be: the $25K that shows up on my 1040, or the annual increase in my net worth?