The payer files it with the IRS and sends you a copy early in the year. Nothing is withheld, which is why a trader receiving large payouts through the year can face a substantial balance plus penalties if estimated-quarterly-taxes were not paid.
Amounts flow to business income, where expenses are deducted and self-employment-tax-prop-payouts applies. Compare the form against your own records: incorrect amounts are best resolved with the payer before filing rather than by quietly reporting a different figure.
A missing 1099-NEC does not make income untaxable. Non-US payers frequently issue nothing at all, and the reporting obligation remains yours.
General information for the United States, not tax advice. Rules change and depend on your circumstances; consult a qualified professional.
Related: self-employment-tax-prop-payouts, estimated-quarterly-taxes, schedule-c-trading-business, prop-firm, payout-split