Income is income and must be reported. If those websites pay you over a certain amount of money, they will send you a tax form as proof. Onlyfans collects money, and they will issue 1099 forms if the person makes more than $600. Premium Snapchat is similar. If they are collecting money directly and forwarding it to the person, they should also issue 1099 forms. This is probably considered a sole proprietorship, and the IRS wants tax on it. They are probably also required to report anything over $400 for Social Security and Medicare taxes. The IRS wants your full income reported. They don't care if you sold drugs, are a cam girl, or sell bundled socks in a flea market. Even if you don't have someone issuing official documents, it is legally required to declare all the income for the year.