Tax remove for some order and keep it for orthers

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We are a payment gateway and we have an app, when we get the order from shopify sometime we need to remove the tax and sometime we dont need that, I tried to remove tax by setting it to null and empty array and setting the customer to tax-exempt but none of those work I get 200 response back  this is the body of the request 

  "order": {
    "id": 2243848437854,
    "total_tax" : 0.00,
    "tax_lines" : [],
    "total_tax_set" : [],
     "customer": {
            "tax_exempt": false
I get 200 response but nothing change in the order.
please if someone can help me with a way that I can achieve this operation and thanks.