Tax ID in the Property Level
Only tax IDs on the agency level is supported, so they are synced to Airbnb. It would be good to have it at the property level so the owner ID can be used.
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Keith commented
The owner isn't collecting the payment, so they're not the one legally responsible for tax reporting.
When you then pay the owner, you issue them a 1099 which shows the IRS that some of your income was paid out to someone else.
If this is for your own records, just use a custom variable and add the owners taxid there, but be careful not to use that variable in a template.
I don't think taxID numbers are synced to airbnb from hostfully in any case, you set your tax id on airbnb's side. if you use the co-host feature, each separate account has their own tax information and airbnb provides appropriate 1099's to whomever was sent money.