diff --git a/include/battle.h b/include/battle.h
index 1ec919c229..758ed7a453 100644
--- a/include/battle.h
+++ b/include/battle.h
@@ -733,7 +733,6 @@ struct BattleStruct
     u8 throwingPokeBall:1;
     u8 ballSpriteIds[2];    // item gfx, window gfx
     u8 moveInfoSpriteId; // move info, window gfx
-    u8 appearedInBattle; // Bitfield to track which Pokemon appeared in battle. Used for Burmy's form change
     u8 skyDropTargets[MAX_BATTLERS_COUNT]; // For Sky Drop, to account for if multiple Pokemon use Sky Drop in a double battle.
     // When using a move which hits multiple opponents which is then bounced by a target, we need to make sure, the move hits both opponents, the one with bounce, and the one without.
     u16 beatUpSpecies[PARTY_SIZE];
diff --git a/src/battle_controller_opponent.c b/src/battle_controller_opponent.c
index 0588d9208b..51322c0315 100644
--- a/src/battle_controller_opponent.c
+++ b/src/battle_controller_opponent.c
@@ -571,14 +571,12 @@ static void OpponentHandleChoosePokemon(u32 battler)
             }
         }
         gBattleStruct->monToSwitchIntoId[battler] = chosenMonId;
-        GetBattlerPartyState(battler)->sentOut = TRUE;
     }
     else
     {
         chosenMonId = gBattleStruct->AI_monToSwitchIntoId[battler];
         gBattleStruct->AI_monToSwitchIntoId[battler] = PARTY_SIZE;
         gBattleStruct->monToSwitchIntoId[battler] = chosenMonId;
-        GetBattlerPartyState(battler)->sentOut = TRUE;
     }
     #if TESTING
     TestRunner_Battle_CheckSwitch(battler, chosenMonId);
diff --git a/src/battle_controller_player_partner.c b/src/battle_controller_player_partner.c
index 58911f1518..2872a83c31 100644
--- a/src/battle_controller_player_partner.c
+++ b/src/battle_controller_player_partner.c
@@ -302,14 +302,12 @@ static void PlayerPartnerHandleChoosePokemon(u32 battler)
             }
         }
         gBattleStruct->monToSwitchIntoId[battler] = chosenMonId;
-        GetBattlerPartyState(battler)->sentOut = TRUE;
     }
     else // Mon to switch out has been already chosen.
     {
         chosenMonId = gBattleStruct->monToSwitchIntoId[battler];
         gBattleStruct->AI_monToSwitchIntoId[battler] = PARTY_SIZE;
         gBattleStruct->monToSwitchIntoId[battler] = chosenMonId;
-        GetBattlerPartyState(battler)->sentOut = TRUE;
     }
     BtlController_EmitChosenMonReturnValue(battler, B_COMM_TO_ENGINE, chosenMonId, NULL);
     BtlController_Complete(battler);
diff --git a/src/battle_main.c b/src/battle_main.c
index cbe58051cb..4591b7575f 100644
--- a/src/battle_main.c
+++ b/src/battle_main.c
@@ -3101,7 +3101,6 @@ static void BattleStartClearSetData(void)
     {
         gSideTimers[i].stickyWebBattlerId = 0xFF;
     }
-    gBattleStruct->appearedInBattle = 0;
     gBattleStruct->beatUpSlot = 0;
 
     for (i = 0; i < PARTY_SIZE; i++)
@@ -3951,12 +3950,7 @@ static void TryDoEventsBeforeFirstTurn(void)
             gBattleCommunication[i] = 0;
 
         for (i = 0; i < gBattlersCount; i++)
-        {
             gBattleMons[i].volatiles.flinched = FALSE;
-            // Record party slots of player's mons that appeared in battle
-            if (!BattlerHasAi(i))
-                gBattleStruct->appearedInBattle |= 1u << gBattlerPartyIndexes[i];
-        }
 
         gBattleStruct->eventBlockCounter = 0;
         gBattleStruct->turnEffectsBattlerId = 0;
@@ -5657,7 +5651,7 @@ static void HandleEndTurn_FinishBattle(void)
             bool8 changedForm = FALSE;
 
             // Appeared in battle and didn't faint
-            if ((gBattleStruct->appearedInBattle & (1u << i)) && GetMonData(&gPlayerParty[i], MON_DATA_HP, NULL) != 0)
+            if (gBattleStruct->partyState[B_SIDE_PLAYER][i].sentOut && GetMonData(&gPlayerParty[i], MON_DATA_HP, NULL) != 0)
                 changedForm = TryFormChange(i, B_SIDE_PLAYER, FORM_CHANGE_END_BATTLE_ENVIRONMENT);
 
             if (!changedForm)
diff --git a/src/battle_script_commands.c b/src/battle_script_commands.c
index 33ca053ad7..8180bb9fbf 100644
--- a/src/battle_script_commands.c
+++ b/src/battle_script_commands.c
@@ -7691,9 +7691,6 @@ static void UpdateSentMonFlags(u32 battler)
 
     gHitMarker &= ~HITMARKER_FAINTED(battler);
     gSpecialStatuses[battler].faintedHasReplacement = FALSE;
-
-    if (!BattlerHasAi(battler))
-        gBattleStruct->appearedInBattle |= 1u << gBattlerPartyIndexes[battler];
 }
 
 static void SetDmgHazardsBattlescript(u8 battler, u8 multistringId)