Merge pull request hotwax#1378 from gauravbhand1611/gauravbhand-ATP-base-rule

Update schedule-atp-rules.md

Author: dt2patel

documents/retail-operations/inventory/available-to-promise/schedule-atp-rules.md

@@ -37,3 +37,15 @@ A balloon icon in the bottom right corner allows retailers to collapse or expand
 {% embed url="https://youtu.be/EYvFXLzoe88" %}
 Change Rule Sequence
 {% endembed %}
+
+## Base Rule
+
+Some inventory rules only apply when a product matches a specific tag or condition. When the product no longer matches that condition, the rule stops applying.
+
+If there’s no other rule available for that product, it gets left in the last assigned state. The last assigned state may not be what the retailer actually wants the default state to be.
+
+Suppose a product has a pre-order tag and requires a different inventory threshold. A rule is created to set the threshold to 10 units for that product. This rule only works for products with the preorder tag.
+
+Now, if the tag is removed from a product, the product won’t qualify for the rule anymore because it no longer has the required tag. However, the threshold of 10 that has been set won't go back to the default level just because the tag is removed.
+
+To avoid this, a base rule can be added to set a default threshold of 5 units for all products. So even if a product loses the preorder tag, it still follows the base rule.