diff --git a/icu4c/source/common/locid.cpp b/icu4c/source/common/locid.cpp
index c0757fc2f2d3..df6211947027 100644
--- a/icu4c/source/common/locid.cpp
+++ b/icu4c/source/common/locid.cpp
@@ -1570,7 +1570,7 @@ AliasReplacer::replaceTransformedExtensions(
              // Split the "tkey-tvalue" pair string so that we can canonicalize the tvalue.
              *const_cast<char*>(tvalue++) = '\0'; // NUL terminate tkey
              output.append(tfield, status).append('-', status);
-             const char* bcpTValue = ulocimp_toBcpType(tfield, tvalue, nullptr, nullptr);
+             const char* bcpTValue = ulocimp_toBcpType(tfield, tvalue);
              output.append((bcpTValue == nullptr) ? tvalue : bcpTValue, status);
         }
     }
diff --git a/icu4c/source/common/uloc.cpp b/icu4c/source/common/uloc.cpp
index 3a4d3b595417..c2b7bbfd6af0 100644
--- a/icu4c/source/common/uloc.cpp
+++ b/icu4c/source/common/uloc.cpp
@@ -2296,7 +2296,7 @@ uloc_toUnicodeLocaleKey(const char* keyword)
 U_CAPI const char* U_EXPORT2
 uloc_toUnicodeLocaleType(const char* keyword, const char* value)
 {
-    const char* bcpType = ulocimp_toBcpType(keyword, value, nullptr, nullptr);
+    const char* bcpType = ulocimp_toBcpType(keyword, value);
     if (bcpType == nullptr && ultag_isUnicodeLocaleType(value, -1)) {
         // unknown keyword, but syntax is fine..
         return value;
@@ -2364,7 +2364,7 @@ uloc_toLegacyKey(const char* keyword)
 U_CAPI const char* U_EXPORT2
 uloc_toLegacyType(const char* keyword, const char* value)
 {
-    const char* legacyType = ulocimp_toLegacyType(keyword, value, nullptr, nullptr);
+    const char* legacyType = ulocimp_toLegacyType(keyword, value);
     if (legacyType == nullptr) {
         // Checks if the specified locale type is well-formed with the legacy locale syntax.
         //
diff --git a/icu4c/source/common/uloc_keytype.cpp b/icu4c/source/common/uloc_keytype.cpp
index e374da450b5c..6ea886ca295c 100644
--- a/icu4c/source/common/uloc_keytype.cpp
+++ b/icu4c/source/common/uloc_keytype.cpp
@@ -449,23 +449,13 @@ ulocimp_toLegacyKey(const char* key) {
 }
 
 U_EXPORT const char*
-ulocimp_toBcpType(const char* key, const char* type, bool* isKnownKey, bool* isSpecialType) {
-    if (isKnownKey != nullptr) {
-        *isKnownKey = false;
-    }
-    if (isSpecialType != nullptr) {
-        *isSpecialType = false;
-    }
-
+ulocimp_toBcpType(const char* key, const char* type) {
     if (!init()) {
         return nullptr;
     }
 
     LocExtKeyData* keyData = static_cast<LocExtKeyData*>(uhash_get(gLocExtKeyMap, key));
     if (keyData != nullptr) {
-        if (isKnownKey != nullptr) {
-            *isKnownKey = true;
-        }
         LocExtType* t = static_cast<LocExtType*>(uhash_get(keyData->typeMap.getAlias(), type));
         if (t != nullptr) {
             return t->bcpId;
@@ -482,9 +472,6 @@ ulocimp_toBcpType(const char* key, const char* type, bool* isKnownKey, bool* isS
                 matched = isSpecialTypeRgKeyValue(type);
             }
             if (matched) {
-                if (isSpecialType != nullptr) {
-                    *isSpecialType = true;
-                }
                 return type;
             }
         }
@@ -494,23 +481,13 @@ ulocimp_toBcpType(const char* key, const char* type, bool* isKnownKey, bool* isS
 
 
 U_EXPORT const char*
-ulocimp_toLegacyType(const char* key, const char* type, bool* isKnownKey, bool* isSpecialType) {
-    if (isKnownKey != nullptr) {
-        *isKnownKey = false;
-    }
-    if (isSpecialType != nullptr) {
-        *isSpecialType = false;
-    }
-
+ulocimp_toLegacyType(const char* key, const char* type) {
     if (!init()) {
         return nullptr;
     }
 
     LocExtKeyData* keyData = static_cast<LocExtKeyData*>(uhash_get(gLocExtKeyMap, key));
     if (keyData != nullptr) {
-        if (isKnownKey != nullptr) {
-            *isKnownKey = true;
-        }
         LocExtType* t = static_cast<LocExtType*>(uhash_get(keyData->typeMap.getAlias(), type));
         if (t != nullptr) {
             return t->legacyId;
@@ -527,9 +504,6 @@ ulocimp_toLegacyType(const char* key, const char* type, bool* isKnownKey, bool*
                 matched = isSpecialTypeRgKeyValue(type);
             }
             if (matched) {
-                if (isSpecialType != nullptr) {
-                    *isSpecialType = true;
-                }
                 return type;
             }
         }
diff --git a/icu4c/source/common/ulocimp.h b/icu4c/source/common/ulocimp.h
index 7fb64062884c..ff3910ac8f35 100644
--- a/icu4c/source/common/ulocimp.h
+++ b/icu4c/source/common/ulocimp.h
@@ -398,10 +398,10 @@ U_EXPORT const char*
 ulocimp_toLegacyKey(const char* key);
 
 U_EXPORT const char*
-ulocimp_toBcpType(const char* key, const char* type, bool* isKnownKey, bool* isSpecialType);
+ulocimp_toBcpType(const char* key, const char* type);
 
 U_EXPORT const char*
-ulocimp_toLegacyType(const char* key, const char* type, bool* isKnownKey, bool* isSpecialType);
+ulocimp_toLegacyType(const char* key, const char* type);
 
 /* Function for testing purpose */
 U_EXPORT const char* const*