主要还是靠自觉

交易全部上1099－K报给IRS，你自己拿1099－K挑着报哪个是收入报税，哪个是代买大衣不用报税。

https://www.forbes.com/advisor/taxes/cash-apps-to-report-payments-of-600-or-more/

Will Venmo, Cash App and Zelle Users Have to Pay a New Tax?

For Venmo, Cash App and other users, this may sound like a new tax—but it’s merely a tax reporting change to the existing tax law.

Form 1099-K is a tax form sent to users that may include both taxable and nontaxable income sources. A taxable source of income is included in your income, such as wages, rents, tips, and retirement income. Whereas a nontaxable source is excluded from your income and you will not need to report on your tax return.

Some examples of nontaxable income are:

• Money received from a friend as a reimbursement
• Money received from a roommate to pay their share of the rent
• Money received from a loved one as a gift

Also, if you receive money from selling a personal item at a loss, you are not required to report the amount on your tax return. For example, if you purchased a dress for $100 and sold it for $50, the amount is not taxable.

But while the new law does not create a new tax, you must keep good records of any taxable income received.