diff --git a/icu4c/source/test/intltest/measfmttest.cpp b/icu4c/source/test/intltest/measfmttest.cpp
index 6da099a2313a..9a6d58286783 100644
--- a/icu4c/source/test/intltest/measfmttest.cpp
+++ b/icu4c/source/test/intltest/measfmttest.cpp
@@ -6116,9 +6116,15 @@ void MeasureFormatTest::TestInvalidIdentifiers() {
         "meter-per-1000-1000",
         "meter-per-1000-second-1000-kilometer",
         "per-1000-and-per-1000",
+        "meter-per-100-100-kilometer", // Failing ICU-23045
     };
 
     for (const auto& input : inputs) {
+        if (uprv_strcmp(input, "meter-per-100-100-kilometer") == 0) {
+            logKnownIssue("ICU-23045", "Incorrect constant denominator for certain unit identifiers "
+                                       "leads to incorrect unit identifiers.");
+            continue;
+        }
         status.setScope(input);
         MeasureUnit::forIdentifier(input, status);
         status.expectErrorAndReset(U_ILLEGAL_ARGUMENT_ERROR);
diff --git a/icu4c/source/test/intltest/units_test.cpp b/icu4c/source/test/intltest/units_test.cpp
index 46ec7d173683..695866e6929e 100644
--- a/icu4c/source/test/intltest/units_test.cpp
+++ b/icu4c/source/test/intltest/units_test.cpp
@@ -1192,6 +1192,7 @@ void UnitsTest::testUnitsConstantsDenomenator() {
     } testCases[]{
         {"meter-per-1000", 1000},
         {"liter-per-1000-kiloliter", 1000},
+        {"meter-per-100-kilometer", 100}, // Failing: ICU-23045
         {"liter-per-kilometer", 0},
         {"second-per-1000-minute", 1000},
         {"gram-per-1000-kilogram", 1000},
@@ -1205,6 +1206,7 @@ void UnitsTest::testUnitsConstantsDenomenator() {
         {"portion-per-7", 7},
         {"portion-per-8", 8},
         {"portion-per-9", 9},
+
         // Test for constant denominators that are powers of 10
         {"portion-per-10", 10},
         {"portion-per-100", 100},
@@ -1214,16 +1216,18 @@ void UnitsTest::testUnitsConstantsDenomenator() {
         {"portion-per-1000000", 1000000},
         {"portion-per-10000000", 10000000},
         {"portion-per-100000000", 100000000},
-        // ICU-22781: {"portion-per-1000000000", 1000000000},
-        // ICU-22781: {"portion-per-10000000000", 10000000000},
-        // ICU-22781: {"portion-per-100000000000", 100000000000},
-        // ICU-22781: {"portion-per-1000000000000", 1000000000000},
-        // ICU-22781: {"portion-per-10000000000000", 10000000000000},
-        // ICU-22781: {"portion-per-100000000000000", 100000000000000},
-        // ICU-22781: {"portion-per-1000000000000000", 1000000000000000},
-        // ICU-22781: {"portion-per-10000000000000000", 10000000000000000},
-        // ICU-22781: {"portion-per-100000000000000000", 100000000000000000},
-        // ICU-22781: {"portion-per-1000000000000000000", 1000000000000000000},
+        {"portion-per-1000000000", 1000000000}, // Failing: ICU-23045
+        {"portion-per-10000000000", 10000000000},
+        {"portion-per-100000000000", 100000000000},
+        {"portion-per-1000000000000", 1000000000000},
+        {"portion-per-10000000000000", 10000000000000},
+        {"portion-per-100000000000000", 100000000000000},
+        {"portion-per-1000000000000000", 1000000000000000},
+        {"portion-per-10000000000000000", 10000000000000000},
+        {"portion-per-100000000000000000", 100000000000000000},
+        {"portion-per-1000000000000000000", 1000000000000000000},
+        {"portion-per-1e3-kilometer", 1000},
+
         // Test for constant denominators that are represented as scientific notation
         // numbers.
         {"portion-per-1e1", 10},
@@ -1238,32 +1242,33 @@ void UnitsTest::testUnitsConstantsDenomenator() {
         {"portion-per-1E5", 100000},
         {"portion-per-1e6", 1000000},
         {"portion-per-1E6", 1000000},
-        // ICU-22781: {"portion-per-1e10", 10000000000},
-        // ICU-22781: {"portion-per-1E10", 10000000000},
-        // ICU-22781: {"portion-per-1e18", 1000000000000000000},
-        // ICU-22781: {"portion-per-1E18", 1000000000000000000},
+        {"portion-per-1e9", 1000000000}, // Failing: ICU-23045
+        {"portion-per-1E9", 1000000000}, // Failing: ICU-23045
+        {"portion-per-1e10", 10000000000},
+        {"portion-per-1E10", 10000000000},
+        {"portion-per-1e18", 1000000000000000000},
+        {"portion-per-1E18", 1000000000000000000},
+
         // Test for constant denominators that are randomly selected.
-        // ICU-22781: {"liter-per-12345-kilometer", 12345},
-        // ICU-22781: {"per-1000-kilometer", 1000},
-        // ICU-22781: {"liter-per-1000-kiloliter", 1000},
+        {"liter-per-12345-kilometer", 12345},
+        {"per-1000-kilometer", 1000},
+        {"liter-per-1000-kiloliter", 1000},
+
         // Test for constant denominators that give 0.
         {"meter", 0},
         {"meter-per-second", 0},
         {"meter-per-square-second", 0},
-        // NOTE: The following constant denominator should be 0. However, since
-        // `100-kilometer` is treated as a unit in CLDR,
-        // the unit does not have a constant denominator.
-        // This issue should be addressed in CLDR.
-        {"meter-per-100-kilometer", 0},
-        // NOTE: the following CLDR identifier should be invalid, but because
-        // `100-kilometer` is considered a unit in CLDR,
-        // one `100` will be considered as a unit constant denominator and the other
-        // `100` will be considered part of the unit.
-        // This issue should be addressed in CLDR.
-        {"meter-per-100-100-kilometer", 100},
     };
 
     for (const auto &testCase : testCases) {
+        if (uprv_strcmp(testCase.source, "portion-per-1000000000") == 0 ||
+            uprv_strcmp(testCase.source, "portion-per-1e9") == 0 ||
+            uprv_strcmp(testCase.source, "portion-per-1E9") == 0 ||
+            uprv_strcmp(testCase.source, "meter-per-100-kilometer") == 0) {
+            logKnownIssue("ICU-23045", "Incorrect constant denominator for certain unit identifiers");
+            continue;
+        }
+
         MeasureUnit unit = MeasureUnit::forIdentifier(testCase.source, status);
         if (status.errIfFailureAndReset("forIdentifier(\"%s\")", testCase.source)) {
             continue;
diff --git a/icu4j/main/common_tests/src/test/java/com/ibm/icu/dev/test/format/MeasureUnitTest.java b/icu4j/main/common_tests/src/test/java/com/ibm/icu/dev/test/format/MeasureUnitTest.java
index 725c061b10e5..be54060cd744 100644
--- a/icu4j/main/common_tests/src/test/java/com/ibm/icu/dev/test/format/MeasureUnitTest.java
+++ b/icu4j/main/common_tests/src/test/java/com/ibm/icu/dev/test/format/MeasureUnitTest.java
@@ -1330,12 +1330,22 @@ class ConstantDenominatorTestCase {
         List<ConstantDenominatorTestCase> testCases = Arrays.asList(
                 new ConstantDenominatorTestCase("meter-per-1000", 1000),
                 new ConstantDenominatorTestCase("liter-per-1000-kiloliter", 1000),
+                new ConstantDenominatorTestCase("meter-per-100-kilometer", 100),
                 new ConstantDenominatorTestCase("liter-per-kilometer", 0),
                 new ConstantDenominatorTestCase("second-per-1000-minute", 1000),
                 new ConstantDenominatorTestCase("gram-per-1000-kilogram", 1000),
-                new ConstantDenominatorTestCase("meter-per-100", 100),
-                // Test for constant denominators that are powers of 10
+                new ConstantDenominatorTestCase("meter-per-100", 100), // Failing ICU-23045
                 new ConstantDenominatorTestCase("portion-per-1", 1),
+                new ConstantDenominatorTestCase("portion-per-2", 2),
+                new ConstantDenominatorTestCase("portion-per-3", 3),
+                new ConstantDenominatorTestCase("portion-per-4", 4),
+                new ConstantDenominatorTestCase("portion-per-5", 5),
+                new ConstantDenominatorTestCase("portion-per-6", 6),
+                new ConstantDenominatorTestCase("portion-per-7", 7),
+                new ConstantDenominatorTestCase("portion-per-8", 8),
+                new ConstantDenominatorTestCase("portion-per-9", 9),
+
+                // Test for constant denominators that are powers of 10
                 new ConstantDenominatorTestCase("portion-per-10", 10),
                 new ConstantDenominatorTestCase("portion-per-100", 100),
                 new ConstantDenominatorTestCase("portion-per-1000", 1000),
@@ -1344,46 +1354,58 @@ class ConstantDenominatorTestCase {
                 new ConstantDenominatorTestCase("portion-per-1000000", 1000000),
                 new ConstantDenominatorTestCase("portion-per-10000000", 10000000),
                 new ConstantDenominatorTestCase("portion-per-100000000", 100000000),
-                // ICU-22781: new ConstantDenominatorTestCase("portion-per-1000000000", 1000000000),
-                // ICU-22781: new ConstantDenominatorTestCase("portion-per-10000000000", 10000000000L),
-                // ICU-22781: new ConstantDenominatorTestCase("portion-per-100000000000", 100000000000L),
-                // ICU-22781: new ConstantDenominatorTestCase("portion-per-1000000000000", 1000000000000L),
-                // ICU-22781: new ConstantDenominatorTestCase("portion-per-10000000000000", 10000000000000L),
-                // ICU-22781: new ConstantDenominatorTestCase("portion-per-100000000000000", 100000000000000L),
-                // ICU-22781: new ConstantDenominatorTestCase("portion-per-1000000000000000", 1000000000000000L),
-                // ICU-22781: new ConstantDenominatorTestCase("portion-per-10000000000000000", 10000000000000000L),
-                // ICU-22781: new ConstantDenominatorTestCase("portion-per-100000000000000000", 100000000000000000L),
-                // ICU-22781: new ConstantDenominatorTestCase("portion-per-1000000000000000000", 1000000000000000000L),
-                // Test for constant denominators that are represented as scientific notation
-                // numbers.
-                // ICU-22781: new ConstantDenominatorTestCase("portion-per-1e9", 1000000000L),
-                // ICU-22781: new ConstantDenominatorTestCase("portion-per-1E9", 1000000000L),
-                // ICU-22781: new ConstantDenominatorTestCase("portion-per-10e9", 10000000000L),
-                // ICU-22781: new ConstantDenominatorTestCase("portion-per-10E9", 10000000000L),
-                // ICU-22781: new ConstantDenominatorTestCase("portion-per-1e10", 10000000000L),
-                // ICU-22781: new ConstantDenominatorTestCase("portion-per-1E10", 10000000000L),
-                // ICU-22781: new ConstantDenominatorTestCase("portion-per-1e3-kilometer", 1000),
-                // Test for constant denominators that are randomely selected.
-                // ICU-22781: new ConstantDenominatorTestCase("liter-per-12345-kilometer", 12345),
-                // ICU-22781: new ConstantDenominatorTestCase("per-1000-kilometer", 1000),
-                // ICU-22781: new ConstantDenominatorTestCase("liter-per-1000-kiloliter", 1000),
-                // Test for constant denominators that gives 0.
-                        new ConstantDenominatorTestCase("meter", 0),
+                new ConstantDenominatorTestCase("portion-per-1000000000", 1000000000), // Failing ICU-23045
+                new ConstantDenominatorTestCase("portion-per-10000000000", 10000000000L),
+                new ConstantDenominatorTestCase("portion-per-100000000000", 100000000000L),
+                new ConstantDenominatorTestCase("portion-per-1000000000000", 1000000000000L),
+                new ConstantDenominatorTestCase("portion-per-10000000000000", 10000000000000L),
+                new ConstantDenominatorTestCase("portion-per-100000000000000", 100000000000000L),
+                new ConstantDenominatorTestCase("portion-per-1000000000000000", 1000000000000000L),
+                new ConstantDenominatorTestCase("portion-per-10000000000000000", 10000000000000000L),
+                new ConstantDenominatorTestCase("portion-per-100000000000000000", 100000000000000000L),
+                new ConstantDenominatorTestCase("portion-per-1000000000000000000", 1000000000000000000L),
+                new ConstantDenominatorTestCase("portion-per-1e3-kilometer", 1000),
+        
+                // Test for constant denominators that are represented as scientific notation numbers.
+                new ConstantDenominatorTestCase("portion-per-1e1", 10),
+                new ConstantDenominatorTestCase("portion-per-1E1", 10),
+                new ConstantDenominatorTestCase("portion-per-1e2", 100),
+                new ConstantDenominatorTestCase("portion-per-1E2", 100),
+                new ConstantDenominatorTestCase("portion-per-1e3", 1000),
+                new ConstantDenominatorTestCase("portion-per-1E3", 1000),
+                new ConstantDenominatorTestCase("portion-per-1e4", 10000),
+                new ConstantDenominatorTestCase("portion-per-1E4", 10000),
+                new ConstantDenominatorTestCase("portion-per-1e5", 100000),
+                new ConstantDenominatorTestCase("portion-per-1E5", 100000),
+                new ConstantDenominatorTestCase("portion-per-1e6", 1000000),
+                new ConstantDenominatorTestCase("portion-per-1E6", 1000000),
+                new ConstantDenominatorTestCase("portion-per-1e9", 1000000000), // Failing ICU-23045
+                new ConstantDenominatorTestCase("portion-per-1E9", 1000000000), // Failing ICU-23045
+                new ConstantDenominatorTestCase("portion-per-1e10", 10000000000L),
+                new ConstantDenominatorTestCase("portion-per-1E10", 10000000000L),
+                new ConstantDenominatorTestCase("portion-per-1e18", 1000000000000000000L),
+                new ConstantDenominatorTestCase("portion-per-1E18", 1000000000000000000L),
+        
+                // Test for constant denominators that are randomly selected.
+                new ConstantDenominatorTestCase("liter-per-12345-kilometer", 12345),
+                new ConstantDenominatorTestCase("per-1000-kilometer", 1000),
+                new ConstantDenominatorTestCase("liter-per-1000-kiloliter", 1000),
+
+                // Test for constant denominators that give 0.
+                new ConstantDenominatorTestCase("meter", 0),
                 new ConstantDenominatorTestCase("meter-per-second", 0),
-                new ConstantDenominatorTestCase("meter-per-square-second", 0),
-                // NOTE: The following constant denominator should be 0. However, since
-                // `100-kilometer` is treated as a unit in CLDR,
-                // the unit does not have a constant denominator.
-                // This issue should be addressed in CLDR.
-                new ConstantDenominatorTestCase("meter-per-100-kilometer", 0),
-                // NOTE: the following CLDR identifier should be invalid, but because
-                // `100-kilometer` is considered a unit in CLDR,
-                // one `100` will be considered as a unit constant denominator and the other
-                // `100` will be considered part of the unit.
-                // This issue should be addressed in CLDR.
-                new ConstantDenominatorTestCase("meter-per-100-100-kilometer", 100));
+                new ConstantDenominatorTestCase("meter-per-square-second", 0));
 
         for (ConstantDenominatorTestCase testCase : testCases) {
+            switch (testCase.identifier) {
+                case "portion-per-1000000000":
+                case "portion-per-1e9":
+                case "portion-per-1E9":
+                case "meter-per-100-kilometer":
+                    logKnownIssue("ICU-23045", "Incorrect constant denominator for certain unit identifiers");
+                    continue;
+            }
+
             MeasureUnit unit = MeasureUnit.forIdentifier(testCase.identifier);
             assertEquals("Constant denominator for " + testCase.identifier, testCase.expectedConstantDenominator,
                     unit.getConstantDenominator());
@@ -1443,9 +1465,16 @@ public void TestInvalidIdentifiers() {
                 "meter-per-1000-second-1000-kilometer",
                 "per-1000-and-per-1000",
                 "liter-per-kilometer-100",
+                "meter-per-100-100-kilometer", // Failing ICU-23045
             };
 
         for (String input : inputs) {
+            if (input.equals("meter-per-100-100-kilometer")) {
+                logKnownIssue("ICU-23045", "Incorrect constant denominator for certain unit identifiers " +
+                        "leads to incorrect unit identifiers.");
+                continue;
+            }
+
             try {
                 MeasureUnit.forIdentifier(input);
                 Assert.fail("An IllegalArgumentException must be thrown");