Exclude Online Marketplace Taxes

I have Shopify Plus integrated with our Avalara instance where all online orders flow into Avalara. I am looking to add other sales channels like TikTok who will pay and remit taxes on my behalf. So orders made on TikTok will flow into our Shopify instance, then into Avalara. How do I flag TikTok orders in Avalara so that taxes are not calculated? Avalara and Shopify support have been extremely unhelpful and frustrating.