diff --git a/lib/data/parse-command-csv-row.js b/lib/data/parse-command-csv-row.js
index 0265cfa65..7ea3f321d 100644
--- a/lib/data/parse-command-csv-row.js
+++ b/lib/data/parse-command-csv-row.js
@@ -3,6 +3,8 @@
 
 'use strict';
 
+const { setDefaultAssertionPriority } = require('../util/assertion-exception');
+
 /**
  * @param {AriaATCSV.Command} commandRow
  * @returns {AriaATParsed.Command}
@@ -186,7 +188,7 @@ function findValuesByKeys(commandsMapping, keysToFind = []) {
   return result;
 }
 
-function parseCommandCSVRowV2({ commands }, commandsJson) {
+function parseCommandCSVRowV2({ commands }, commandsJson, assertions) {
   const commandsParsed = [];
   const flattenedCommandsJson = flattenObject(commandsJson);
 
@@ -195,7 +197,10 @@ function parseCommandCSVRowV2({ commands }, commandsJson) {
     const commandKVs = findValuesByKeys(flattenedCommandsJson, [command.command]);
 
     const assertionExceptions = command.assertionExceptions.length
-      ? sanitizeWhitespace(command.assertionExceptions).split(' ')
+      ? setDefaultAssertionPriority(
+          sanitizeWhitespace(command.assertionExceptions),
+          assertions
+        ).split(' ')
       : [];
 
     const commands = commandKVs.map(e => ({
diff --git a/lib/data/parse-test-csv-row.js b/lib/data/parse-test-csv-row.js
index 4fdd791ce..c20ec8e77 100644
--- a/lib/data/parse-test-csv-row.js
+++ b/lib/data/parse-test-csv-row.js
@@ -3,6 +3,8 @@
 
 'use strict';
 
+const { setDefaultAssertionPriority } = require('../util/assertion-exception');
+
 /**
  * @param {AriaATCSV.Test} testRow
  * @returns {AriaATParsed.Test}
@@ -216,12 +218,16 @@ function parseTestCSVRowV2({ tests, assertions, scripts, commands }) {
             at => at.key === key && at.settings === (command.settings || 'defaultMode')
           )
         ) {
+          const assertionExceptions = setDefaultAssertionPriority(
+            command.assertionExceptions,
+            assertions
+          );
           const commandInfo = {
             testId: command.testId,
             command: command.command,
             settings: command.settings || 'defaultMode',
             presentationNumber: Number(command.presentationNumber),
-            assertionExceptions: command.assertionExceptions,
+            assertionExceptions: assertionExceptions,
           };
 
           // Test level commandInfo, useful for getting assertionExceptions and
diff --git a/lib/data/process-test-directory/index.js b/lib/data/process-test-directory/index.js
index 4723175df..f3b8d4d35 100644
--- a/lib/data/process-test-directory/index.js
+++ b/lib/data/process-test-directory/index.js
@@ -197,7 +197,7 @@ const processTestDirectory = async config => {
   }
 
   const validCommandKeys = /^(?:testId|command|settings|assertionExceptions|presentationNumber)$/;
-  const assertionsExceptionsFormat = /^([0123]:[a-zA-Z-\d]+\s*)+$/;
+  const assertionsExceptionsFormat = /^(([0123]:)?[a-zA-Z-\d]+\s*)+$/;
   const settingsFormat = /^[A-Za-z0-9-\s]+$/;
   function validateCommandsKeys(row) {
     // example header:
@@ -557,7 +557,8 @@ const processTestDirectory = async config => {
     {
       commands: parsedAtCommandsCsvs,
     },
-    commandsJson
+    commandsJson,
+    assertionsCsv
   );
   const {
     references: { aria, htmlAam },
diff --git a/lib/util/assertion-exception.js b/lib/util/assertion-exception.js
new file mode 100644
index 000000000..88a6a65f7
--- /dev/null
+++ b/lib/util/assertion-exception.js
@@ -0,0 +1,38 @@
+/**
+ * Generates the assertionException string with a default priority prefix
+ * @param {String} assertionException
+ * @param {Number} defaultPriority
+ * @returns {String}
+ */
+function setDefaultAssertionException(assertionException, defaultPriority) {
+  if (assertionException && !assertionException.includes(':')) {
+    return `${defaultPriority}:${assertionException}`;
+  }
+  return assertionException;
+}
+
+/**
+ * Finds the default assertion value for an assertionException without
+ * a priority prefix in a string of assertionExceptions and recreates
+ * the string with the new default assertion priorities
+ * @param {String} assertionExceptions
+ * @param {Array} assertions
+ * @returns {String}
+ */
+function setDefaultAssertionPriority(assertionExceptions, assertions) {
+  return assertionExceptions
+    .split(' ')
+    .map(assertionException => {
+      const assertion = assertions.find(assertion =>
+        assertionException.includes(assertion.assertionId)
+      );
+      if (assertion) {
+        const defaultPriority = assertion.priority;
+        return setDefaultAssertionException(assertionException, defaultPriority);
+      }
+      return assertionException;
+    })
+    .join(' ');
+}
+
+exports.setDefaultAssertionPriority = setDefaultAssertionPriority;