diff --git a/scripts/JSON_data_files_validator.py b/scripts/JSON_data_files_validator.py
index 63daa81e21..bacf268dde 100644
--- a/scripts/JSON_data_files_validator.py
+++ b/scripts/JSON_data_files_validator.py
@@ -115,7 +115,8 @@ def _get_valid_schema(self) -> Schema:
                                 },
                                 'bytes': float
                             }
-                        ]
+                        ],
+                        Optional('user_defined'): dict
                     },
                 ]
             }
diff --git a/src/vt/phase/phase_manager.h b/src/vt/phase/phase_manager.h
index 62f209a100..4e8591eff8 100644
--- a/src/vt/phase/phase_manager.h
+++ b/src/vt/phase/phase_manager.h
@@ -49,6 +49,7 @@
 #include "vt/phase/phase_hook_enum.h"
 #include "vt/phase/phase_hook_id.h"
 #include "vt/vrt/collection/balance/lb_invoke/phase_info.h"
+#include "vt/vrt/collection/balance/node_lb_data.h"
 
 #include <unordered_map>
 #include <map>
@@ -169,6 +170,36 @@ struct PhaseManager : runtime::component::Component<PhaseManager> {
    */
   void setStartTime();
 
+
+template <typename T, typename = void>
+struct is_jsonable : std::false_type {};
+
+template <typename T>
+struct is_jsonable<T, std::void_t<decltype(nlohmann::json(std::declval<T>()))>> : std::true_type {};
+
+template <typename KeyT, typename ValueT>
+void addUserDefinedData(PhaseType phase, const KeyT& key, const ValueT& value) {
+  static_assert(
+    is_jsonable<KeyT>::value,
+    "PhaseManager::addUserDefinedData: KeyT type is not jsonable"
+  );
+  static_assert(
+    is_jsonable<ValueT>::value,
+    "PhaseManager::addUserDefinedData: ValueT type is not jsonable"
+  );
+
+  auto perPhase = theNodeLBData()->getLBData()->user_per_phase_json_;
+
+  if (perPhase.find(phase) == perPhase.end()) {
+    auto j = std::make_shared<nlohmann::json>();
+    j->emplace(key, value);
+
+    theNodeLBData()->getLBData()->user_per_phase_json_[phase] = j;
+  } else {
+    perPhase[phase]->emplace(key, value);
+  }
+}
+
   /**
    * \brief Print summary for the current phase.
    *
diff --git a/src/vt/vrt/collection/balance/lb_data_holder.cc b/src/vt/vrt/collection/balance/lb_data_holder.cc
index 3f0da67f2a..d679c70fdb 100644
--- a/src/vt/vrt/collection/balance/lb_data_holder.cc
+++ b/src/vt/vrt/collection/balance/lb_data_holder.cc
@@ -218,6 +218,14 @@ std::unique_ptr<nlohmann::json> LBDataHolder::toJson(PhaseType phase) const {
     }
   }
 
+  if (user_per_phase_json_.find(phase) != user_per_phase_json_.end()) {
+    auto& user_def_this_phase = user_per_phase_json_.at(phase);
+
+    if (!user_def_this_phase->empty()) {
+      j["user_defined"] = *user_def_this_phase;
+    }
+  }
+
   return std::make_unique<json>(std::move(j));
 }
 
@@ -362,6 +370,12 @@ LBDataHolder::LBDataHolder(nlohmann::json const& j)
           }
         }
       }
+
+      if (phase.find("user_defined") != phase.end()) {
+        auto userDefined = phase["user_defined"];
+        user_per_phase_json_[phase] = std::make_shared<nlohmann::json>();
+        *(user_per_phase_json_[phase]) = userDefined;
+      }
     }
   }
 
diff --git a/src/vt/vrt/collection/balance/lb_data_holder.h b/src/vt/vrt/collection/balance/lb_data_holder.h
index f12a614426..3a69999d98 100644
--- a/src/vt/vrt/collection/balance/lb_data_holder.h
+++ b/src/vt/vrt/collection/balance/lb_data_holder.h
@@ -79,6 +79,7 @@ struct LBDataHolder {
     s | node_comm_;
     s | node_subphase_comm_;
     s | user_defined_json_;
+    s | user_per_phase_json_;
     s | node_idx_;
     s | count_;
     s | skipped_phases_;
@@ -134,6 +135,8 @@ struct LBDataHolder {
   std::unordered_map<PhaseType, std::unordered_map<
     ElementIDStruct, std::shared_ptr<nlohmann::json>
   >> user_defined_json_;
+
+  std::unordered_map<PhaseType, std::shared_ptr<nlohmann::json>> user_per_phase_json_;
   /// User-defined data from each phase for LB
   std::unordered_map<PhaseType, DataMapType> user_defined_lb_info_;
   /// Node indices for each ID along with the proxy ID
diff --git a/tests/unit/collection/test_lb.extended.cc b/tests/unit/collection/test_lb.extended.cc
index 0d01f82dca..d9d0dd199c 100644
--- a/tests/unit/collection/test_lb.extended.cc
+++ b/tests/unit/collection/test_lb.extended.cc
@@ -408,6 +408,12 @@ TEST_P(TestNodeLBDataDumper, test_node_lb_data_dumping_with_interval) {
       proxy.broadcastCollective<colHandler>();
     });
 
+    vt::thePhase()->addUserDefinedData(
+      phase, std::string{"time"}, static_cast<double>(phase));
+
+    vt::thePhase()->addUserDefinedData(
+      phase, std::string{"new_time"}, static_cast<double>(phase));
+
     // Go to the next phase
     vt::thePhase()->nextPhaseCollective();
   }
@@ -424,6 +430,14 @@ TEST_P(TestNodeLBDataDumper, test_node_lb_data_dumping_with_interval) {
 
     EXPECT_TRUE(json.find("phases") != json.end());
     EXPECT_EQ(json["phases"].size(), num_phases);
+    for(const auto& phase : json["phases"]){
+      EXPECT_TRUE(phase.find("user_defined") != phase.end());
+      EXPECT_TRUE(phase["user_defined"].contains("time"));
+      EXPECT_EQ(phase["user_defined"]["time"], static_cast<double>(phase["id"]));
+      EXPECT_TRUE(phase["user_defined"].contains("new_time"));
+      EXPECT_EQ(phase["user_defined"]["new_time"], static_cast<double>(phase["id"]));
+    }
+
   });
 
   if (vt::theContext()->getNode() == 0) {