diff --git a/components/brave_news/browser/brave_news_p3a.cc b/components/brave_news/browser/brave_news_p3a.cc
index c23daa3e0a48..e1a7fd039ee3 100644
--- a/components/brave_news/browser/brave_news_p3a.cc
+++ b/components/brave_news/browser/brave_news_p3a.cc
@@ -120,7 +120,7 @@ void NewsMetrics::RecordTotalActionCount(ActionType action,
                                          uint64_t count_delta) {
   DVLOG(1) << __FUNCTION__ << " action: " << static_cast<int>(action)
            << ", count_delta: " << count_delta;
-  const char* pref_name;
+  const char* pref_name = nullptr;
   switch (action) {
     case ActionType::kCardView:
       pref_name = prefs::kBraveNewsTotalCardViews;
@@ -131,10 +131,8 @@ void NewsMetrics::RecordTotalActionCount(ActionType action,
     case ActionType::kSidebarFilterUsage:
       pref_name = prefs::kBraveNewsTotalSidebarFilterUsages;
       break;
-    default:
-      NOTREACHED_IN_MIGRATION();
-      return;
   }
+  CHECK(pref_name);
 
   WeeklyStorage total_storage(prefs_, pref_name);
 
@@ -164,8 +162,6 @@ void NewsMetrics::RecordTotalActionCount(ActionType action,
       p3a_utils::RecordToHistogramBucket(kSidebarFilterUsageHistogramName,
                                          kSidebarFilterUsageBuckets, total);
       break;
-    default:
-      NOTREACHED_IN_MIGRATION();
   }
 }
 
@@ -204,7 +200,7 @@ void NewsMetrics::RecordTotalSubscribedCount(SubscribeType subscribe_type,
     subscription_counts_[subscribe_type] = *total;
   }
 
-  const char* histogram_name;
+  const char* histogram_name = nullptr;
   switch (subscribe_type) {
     case SubscribeType::kChannels:
       histogram_name = kChannelCountHistogramName;
@@ -212,10 +208,8 @@ void NewsMetrics::RecordTotalSubscribedCount(SubscribeType subscribe_type,
     case SubscribeType::kPublishers:
       histogram_name = kPublisherCountHistogramName;
       break;
-    default:
-      NOTREACHED_IN_MIGRATION();
-      return;
   }
+  CHECK(histogram_name);
 
   if (!IsMonthlyActiveUser()) {
     // Only report for active users in the past month.
diff --git a/components/brave_wallet/browser/brave_wallet_p3a.cc b/components/brave_wallet/browser/brave_wallet_p3a.cc
index 4291f979e172..c17d9549e610 100644
--- a/components/brave_wallet/browser/brave_wallet_p3a.cc
+++ b/components/brave_wallet/browser/brave_wallet_p3a.cc
@@ -147,7 +147,7 @@ void BraveWalletP3A::ReportJSProvider(mojom::JSProviderType provider_type,
       histogram_name = kSolProviderHistogramName;
       break;
     default:
-      NOTREACHED_NORETURN();
+      return;
   }
 
   JSProviderAnswer answer = JSProviderAnswer::kNoWallet;
@@ -180,8 +180,6 @@ void BraveWalletP3A::ReportJSProvider(mojom::JSProviderType provider_type,
                      : JSProviderAnswer::kNativeNotOverridden;
       }
       break;
-    default:
-      NOTREACHED_NORETURN();
   }
 
   base::UmaHistogramEnumeration(histogram_name, answer);
@@ -256,12 +254,9 @@ void BraveWalletP3A::ReportTransactionSent(mojom::CoinType coin,
     case mojom::CoinType::ZEC:
       histogram_name = kZecTransactionSentHistogramName;
       break;
-    default:
-      NOTREACHED_IN_MIGRATION() << coin;
-      return;
   }
 
-  DCHECK(histogram_name);
+  CHECK(histogram_name);
 
   ScopedDictPrefUpdate last_sent_time_update(
       profile_prefs_, kBraveWalletLastTransactionSentTimeDict);
@@ -309,12 +304,9 @@ void BraveWalletP3A::RecordActiveWalletCount(int count,
     case mojom::CoinType::ZEC:
       histogram_name = kZecActiveAccountHistogramName;
       break;
-    default:
-      NOTREACHED_IN_MIGRATION() << coin_type;
-      return;
   }
 
-  DCHECK(histogram_name);
+  CHECK(histogram_name);
 
   const base::Value::Dict& active_wallet_dict =
       profile_prefs_->GetDict(kBraveWalletP3AActiveWalletDict);
@@ -472,7 +464,7 @@ void BraveWalletP3A::OnTransactionStatusChanged(
       return;
     }
   } else {
-    NOTREACHED_IN_MIGRATION();
+    return;
   }
   ReportTransactionSent(tx_coin, true);
 }
diff --git a/components/misc_metrics/menu_metrics.cc b/components/misc_metrics/menu_metrics.cc
index edc21a03d85f..e54d7862d4c4 100644
--- a/components/misc_metrics/menu_metrics.cc
+++ b/components/misc_metrics/menu_metrics.cc
@@ -37,7 +37,7 @@ const char* GetMenuGroupPrefKey(MenuGroup group) {
     case MenuGroup::kBrowserViews:
       return kBrowserViewsPrefKey;
   }
-  NOTREACHED_IN_MIGRATION();
+  NOTREACHED();
 }
 
 }  // namespace
diff --git a/components/p3a/constellation_helper_unittest.cc b/components/p3a/constellation_helper_unittest.cc
index 4635c228b321..f5471852b52c 100644
--- a/components/p3a/constellation_helper_unittest.cc
+++ b/components/p3a/constellation_helper_unittest.cc
@@ -125,7 +125,7 @@ class P3AConstellationHelperTest : public testing::Test {
       case MetricLogType::kExpress:
         return kTestExpressEpoch;
     }
-    NOTREACHED_IN_MIGRATION();
+    NOTREACHED();
   }
 
   const char* GetTestNextEpochTime(MetricLogType log_type) {
@@ -137,7 +137,7 @@ class P3AConstellationHelperTest : public testing::Test {
       case MetricLogType::kExpress:
         return kTestExpressNextEpochTime;
     }
-    NOTREACHED_IN_MIGRATION();
+    NOTREACHED();
   }
 
   void CheckInfoRequestMade(MetricLogType log_type) {
diff --git a/components/p3a/constellation_log_store.cc b/components/p3a/constellation_log_store.cc
index faf80b1d9319..dcfa9b48711f 100644
--- a/components/p3a/constellation_log_store.cc
+++ b/components/p3a/constellation_log_store.cc
@@ -130,18 +130,15 @@ const std::string& ConstellationLogStore::staged_log_histogram_name() const {
 }
 
 const std::string& ConstellationLogStore::staged_log_hash() const {
-  NOTREACHED_IN_MIGRATION();
-  return staged_log_hash_;
+  NOTREACHED();
 }
 
 const std::string& ConstellationLogStore::staged_log_signature() const {
-  NOTREACHED_IN_MIGRATION();
-  return staged_log_signature_;
+  NOTREACHED();
 }
 
 std::optional<uint64_t> ConstellationLogStore::staged_log_user_id() const {
-  NOTREACHED_IN_MIGRATION();
-  return std::nullopt;
+  NOTREACHED();
 }
 
 void ConstellationLogStore::StageNextLog() {
@@ -175,7 +172,7 @@ void ConstellationLogStore::MarkStagedLogAsSent() {
 
 void ConstellationLogStore::TrimAndPersistUnsentLogs(
     bool overwrite_in_memory_store) {
-  NOTREACHED_IN_MIGRATION();
+  NOTREACHED();
 }
 
 size_t ConstellationLogStore::GetMaxEpochsToRetain() const {
diff --git a/components/p3a/constellation_log_store_unittest.cc b/components/p3a/constellation_log_store_unittest.cc
index 22388268b69b..3ac8633ff0e8 100644
--- a/components/p3a/constellation_log_store_unittest.cc
+++ b/components/p3a/constellation_log_store_unittest.cc
@@ -42,7 +42,7 @@ class P3AConstellationLogStoreTest : public testing::Test {
       case MetricLogType::kExpress:
         return kExpressMaxEpochsToRetain;
     }
-    NOTREACHED_IN_MIGRATION();
+    NOTREACHED();
   }
 
   void UpdateSomeMessages(uint8_t epoch, size_t message_count) {
diff --git a/components/p3a/histograms_braveizer.cc b/components/p3a/histograms_braveizer.cc
index 40d0aec157a9..f625ab6426a2 100644
--- a/components/p3a/histograms_braveizer.cc
+++ b/components/p3a/histograms_braveizer.cc
@@ -71,7 +71,7 @@ void HistogramsBraveizer::DoHistogramBravetization(
         answer = 1;
         break;
       default:
-        NOTREACHED_IN_MIGRATION();
+        return;
     }
     UMA_HISTOGRAM_BOOLEAN("Brave.Core.IsDefault", answer);
   }
diff --git a/components/p3a/message_manager_unittest.cc b/components/p3a/message_manager_unittest.cc
index 6b7066237f86..3f82d9d94d99 100644
--- a/components/p3a/message_manager_unittest.cc
+++ b/components/p3a/message_manager_unittest.cc
@@ -207,7 +207,7 @@ class P3AMessageManagerTest : public testing::Test,
         histogram_names_end = kCollectedTypicalHistograms.cend();
         break;
       default:
-        NOTREACHED_IN_MIGRATION();
+        NOTREACHED();
     }
     for (auto histogram_name_i = histogram_names_begin;
          histogram_name_i != histogram_names_end; histogram_name_i++) {
diff --git a/components/p3a/metric_log_store.cc b/components/p3a/metric_log_store.cc
index 3251111a42e2..92e11bb4eeb8 100644
--- a/components/p3a/metric_log_store.cc
+++ b/components/p3a/metric_log_store.cc
@@ -219,18 +219,15 @@ const std::string& MetricLogStore::staged_log_key() const {
 }
 
 const std::string& MetricLogStore::staged_log_hash() const {
-  NOTREACHED_IN_MIGRATION();
-  return staged_log_hash_;
+  NOTREACHED();
 }
 
 const std::string& MetricLogStore::staged_log_signature() const {
-  NOTREACHED_IN_MIGRATION();
-  return staged_log_signature_;
+  NOTREACHED();
 }
 
 std::optional<uint64_t> MetricLogStore::staged_log_user_id() const {
-  NOTREACHED_IN_MIGRATION();
-  return std::nullopt;
+  NOTREACHED();
 }
 
 void MetricLogStore::StageNextLog() {
@@ -277,7 +274,7 @@ void MetricLogStore::DiscardStagedLog(std::string_view reason) {
 void MetricLogStore::MarkStagedLogAsSent() {}
 
 void MetricLogStore::TrimAndPersistUnsentLogs(bool overwrite_in_memory_store) {
-  NOTREACHED_IN_MIGRATION();
+  NOTREACHED();
 }
 
 void MetricLogStore::LoadPersistedUnsentLogs() {
diff --git a/components/p3a/metric_log_type.cc b/components/p3a/metric_log_type.cc
index 9ab4d1ffc672..8de38a4661cc 100644
--- a/components/p3a/metric_log_type.cc
+++ b/components/p3a/metric_log_type.cc
@@ -26,7 +26,7 @@ const char* MetricLogTypeToString(MetricLogType log_type) {
     case MetricLogType::kExpress:
       return kExpressStr;
   }
-  NOTREACHED_IN_MIGRATION();
+  NOTREACHED();
 }
 
 std::optional<MetricLogType> StringToMetricLogType(
diff --git a/components/p3a/p3a_service.cc b/components/p3a/p3a_service.cc
index 4b2dcecd1f00..52f538703199 100644
--- a/components/p3a/p3a_service.cc
+++ b/components/p3a/p3a_service.cc
@@ -270,7 +270,6 @@ void P3AService::OnHistogramChanged(const char* histogram_name,
   const bool ok = samples->Iterator()->GetBucketIndex(&bucket);
   if (!ok) {
     LOG(ERROR) << "Only linear histograms are supported at the moment!";
-    NOTREACHED_IN_MIGRATION();
     return;
   }
 
diff --git a/components/p3a/rotation_scheduler.cc b/components/p3a/rotation_scheduler.cc
index 0c9ee8ee253e..d27954576cca 100644
--- a/components/p3a/rotation_scheduler.cc
+++ b/components/p3a/rotation_scheduler.cc
@@ -77,7 +77,7 @@ base::Time GetNextJsonRotationTime(MetricLogType log_type,
     case MetricLogType::kExpress:
       return NextDay(last_rotation);
     default:
-      NOTREACHED_IN_MIGRATION();
+      NOTREACHED();
   }
 }
 
@@ -90,9 +90,8 @@ const char* GetJsonRotationTimestampPref(MetricLogType log_type) {
     case MetricLogType::kExpress:
       return kLastExpressJsonRotationTimeStampPref;
     default:
-      NOTREACHED_IN_MIGRATION();
+      NOTREACHED();
   }
-  return nullptr;
 }
 
 const char* GetConstellationRotationTimestampPref(MetricLogType log_type) {
@@ -104,9 +103,8 @@ const char* GetConstellationRotationTimestampPref(MetricLogType log_type) {
     case MetricLogType::kExpress:
       return kLastExpressConstellationRotationTimeStampPref;
     default:
-      NOTREACHED_IN_MIGRATION();
+      NOTREACHED();
   }
-  return nullptr;
 }
 
 }  // namespace