diff --git a/account_avatax_sale_oca/models/sale_order.py b/account_avatax_sale_oca/models/sale_order.py
index 599ee084a..fa544e7d8 100644
--- a/account_avatax_sale_oca/models/sale_order.py
+++ b/account_avatax_sale_oca/models/sale_order.py
@@ -89,7 +89,6 @@ def onchange_reset_avatax_amount(self):
         """
         for order in self:
             order.tax_amount = 0
-            order.order_line.tax_amt = 0
 
     @api.depends("order_line.price_total", "order_line.product_uom_qty", "tax_amount")
     def _compute_amounts(self):
@@ -293,6 +292,8 @@ def write(self, vals):
         result = super(SaleOrder, self).write(vals)
         avatax_config = self.env.company.get_avatax_config_company()
         for record in self:
+            if not record.tax_amount:
+                record.order_line.write({"tax_amt": 0})
             if (
                 avatax_config.sale_calculate_tax
                 and record.calculate_tax_on_save
diff --git a/account_avatax_sale_oca/tests/__init__.py b/account_avatax_sale_oca/tests/__init__.py
new file mode 100644
index 000000000..6f699d0d8
--- /dev/null
+++ b/account_avatax_sale_oca/tests/__init__.py
@@ -0,0 +1 @@
+from . import test_sale_order
diff --git a/account_avatax_sale_oca/tests/test_sale_order.py b/account_avatax_sale_oca/tests/test_sale_order.py
new file mode 100644
index 000000000..25f46bf6e
--- /dev/null
+++ b/account_avatax_sale_oca/tests/test_sale_order.py
@@ -0,0 +1,82 @@
+# Copyright 2021 Open Source Integrators
+# License AGPL-3 - See http://www.gnu.org/licenses/agpl-3.0.html
+
+
+from odoo.fields import Command
+from odoo.tests import Form, common
+
+
+class TestSaleOrder(common.TransactionCase):
+    @classmethod
+    def setUpClass(cls):
+        super().setUpClass()
+        cls.partner = cls.env["res.partner"].create(
+            {
+                "name": "Test Customer",
+            }
+        )
+        cls.empty_order = cls.env["sale.order"].create(
+            {
+                "partner_id": cls.partner.id,
+            }
+        )
+        cls.product = cls.env["product.product"].create({"name": "Super Product"})
+
+    def test_sale_order_onchange(self):
+        """We found a bug where the price when the decimal accuracy was 5,
+        the price would be automatically reset to the pricelist price after
+        saving the order. The reason was a wrong implementation of
+        onchange_reset_avatax_amount. In this test we demonstrate that
+        the error does not happen anymore."""
+        # Change accuracy of product unit of measure
+        self.env.ref("product.decimal_product_uom").digits = 5
+        # Enable pricelists
+        self.env.user.groups_id += self.env.ref("product.group_product_pricelist")
+        self.pricelist = self.env["product.pricelist"].create(
+            {
+                "name": "Test pricelist",
+                "discount_policy": "without_discount",
+                "item_ids": [
+                    Command.create(
+                        {
+                            "base": "list_price",
+                            "min_quantity": 6,
+                            "product_id": self.product.id,
+                            "compute_price": "fixed",
+                            "fixed_price": 20,
+                        }
+                    ),
+                ],
+            }
+        )
+        so = self.empty_order
+        so_form = Form(so)
+        so_form.pricelist_id = self.pricelist
+        with so_form.order_line.new() as line:
+            line.product_id = self.product
+            line.product_uom_qty = 7.0
+        so_form.save()
+        with so_form.order_line.new() as line:
+            line.product_id = self.product
+            line.product_uom_qty = 7.0
+        so_form.save()
+        with Form(so) as so_form:
+            with so_form.order_line.edit(0) as line0_form:
+                line0_form.price_unit = 100.00000
+            with so_form.order_line.edit(1) as line1_form:
+                line1_form.price_unit = 100.00000
+        so_form.save()
+        self.assertEqual(so.tax_amount, 0.0)
+        self.assertEqual(so.order_line[0].price_unit, 100.00000)
+        self.assertEqual(so.order_line[0].tax_amt, 0.0)
+        self.assertEqual(so.order_line[1].price_unit, 100.00000)
+        self.assertEqual(so.order_line[1].tax_amt, 0.0)
+        with Form(so) as so_form:
+            with so_form.order_line.edit(1) as line1_form:
+                line1_form.price_unit = 200.00000
+        so_form.save()
+        self.assertEqual(so.tax_amount, 0.0)
+        self.assertEqual(so.order_line[0].price_unit, 100.00000)
+        self.assertEqual(so.order_line[0].tax_amt, 0.0)
+        self.assertEqual(so.order_line[1].price_unit, 200.00000)
+        self.assertEqual(so.order_line[1].tax_amt, 0.0)