理論上，他們不付稅你就要扣稅。
request W9 before payment -> if yes, issue 1099-NEC -> if not, 28% withholding.
https://polittelaw.com/blog/what-if-a-contractor-or-vendor-refuses-to-provide-a-w-9-for-a-1099/
What if a payee refuses or neglects to provide a TIN?
If a payee refuses or neglects to provide a TIN when properly requested by a business, the business should immediately begin backup withholding, at the rate of 28 percent, on any reportable payments made to the payee (and remit this amount to the IRS).
The business should also make up to three solicitations to the payee for the payee’s TIN, in order to avoid a penalty for failing to include a TIN on the Form 1099 information return filed by the business.
Finally, if a contractor, vendor, or other payee refuses or fails to provide his taxpayer identification number, the business should still fill out and timely file its 1099 information return(s) with a notation that the payee failed or refused to provide his taxpayer identification number. Failure to file Form 1099 based on a person’s refusal or failure to provide his taxpayer identification number does not excuse the business from timely filing all required information returns.
