Create Order using API and automatically include Tax

Retired Boards Appdev Custom Storefronts
,
1

Hi there. I am using Order Creation API and I want to include the tax lines as well. When I am creating the tax manually, then it is adding the Tax but when I am using the API, it is not adding automatically.

Secondly , I tried adding the
“tax_lines”: [
{
“title”: “VAT”,
“rate”: “0.15”,
“price”:“12”
}
],

But the problem is I can’t determine what will be the PRICE of the tax. Is there a way I can make shopify add the tax automatically?