But don't you have to prove you are taking a loss or coming out even via actual receipts?
No because it doesn't matter unless you have a business. The majority of us won't have what qualifies as a business under IRS scrutiny, so there are no expenses to consider. Meaning you get taxed on the earnings with no deduction for expenses. Unless they changed guidelines for a business as well.
These are the characteristics of a business according to the IRS:
Whether you carry on the activity in a businesslike manner and maintain complete and accurate books and records.
Whether you have personal motives in carrying on the activity.
Whether the time and effort you put into the activity indicate you intend to make it profitable.
Whether you depend on income from the activity for your livelihood.
Whether your losses are due to circumstances beyond your control (or are normal in the startup phase of your type of business).
Whether you or your advisors have the knowledge needed to carry on the activity as a successful business.
Whether you were successful in making a profit in similar activities in the past.
Whether the activity makes a profit in some years and how much profit it makes.
Whether you can expect to make a future profit from the appreciation of the assets used in the activity.