grammar - What is the difference between 〜となる and 〜になる?

Is it a nuance difference? Is it formality?

EDIT

For example:

請求書のお支払いは現金のみとなりますので、ご了承くださいませ。

請求書のお支払いは現金のみになりますので、ご了承くださいませ。

I just made that example up, but for some reason, my gut tells me it's the first one, even though I don't see anything grammatically wrong with the second, either. Is it formality level only?

Answer

Pretty finely nuanced, I'd say. と is a quotative particle, but is also used to described the manner in which something is done, often figurative. ～となる can be used to mean "become like a ~" while ～になる is literally "become a ~".