Business & farm

I understand that capital contribution as a sole-prop is not income and is, as you mentioned, just moving money from your left pocket to your right. But my question is this: do you need to show how much capital you've contributed on your taxes, even if it's just for reference? Let's say you put $3000 cash in your business account, money that came out of your own pocket. How does the IRS know that money wasn't income?