diff --git a/app/Domain/UserVacationStatsRetriever.php b/app/Domain/UserVacationStatsRetriever.php
index 8d1e66d..3a8a6e6 100644
--- a/app/Domain/UserVacationStatsRetriever.php
+++ b/app/Domain/UserVacationStatsRetriever.php
@@ -21,7 +21,7 @@ class UserVacationStatsRetriever
     {
         return $user
             ->vacations()
-            ->where("year_period_id", $yearPeriod->id)
+            ->whereBelongsTo($yearPeriod)
             ->whereRelation(
                 "vacationRequest",
                 fn(Builder $query) => $query
@@ -37,7 +37,7 @@ class UserVacationStatsRetriever
             ->whereRelation(
                 "vacationRequest",
                 fn(Builder $query) => $query
-                    ->where("year_period_id", $yearPeriod->id)
+                    ->whereBelongsTo($yearPeriod)
                     ->whereIn("type", $this->getLimitableVacationTypes())
                     ->states(VacationRequestStatesRetriever::successStates()),
             )
@@ -50,7 +50,7 @@ class UserVacationStatsRetriever
     {
         return $user
             ->vacations()
-            ->where("year_period_id", $yearPeriod->id)
+            ->whereBelongsTo($yearPeriod)
             ->whereRelation(
                 "vacationRequest",
                 fn(Builder $query) => $query
@@ -64,7 +64,7 @@ class UserVacationStatsRetriever
     {
         return $user
             ->vacations()
-            ->where("year_period_id", $yearPeriod->id)
+            ->whereBelongsTo($yearPeriod)
             ->whereRelation(
                 "vacationRequest",
                 fn(Builder $query) => $query
@@ -86,7 +86,7 @@ class UserVacationStatsRetriever
     public function getVacationDaysLimit(User $user, YearPeriod $yearPeriod): int
     {
         $limit = $user->vacationLimits()
-            ->where("year_period_id", $yearPeriod->id)
+            ->whereBelongsTo($yearPeriod)
             ->first()
             ?->days;
 
diff --git a/app/Domain/Validation/Rules/DoesNotExceedLimitRule.php b/app/Domain/Validation/Rules/DoesNotExceedLimitRule.php
index c835cf6..3e90472 100644
--- a/app/Domain/Validation/Rules/DoesNotExceedLimitRule.php
+++ b/app/Domain/Validation/Rules/DoesNotExceedLimitRule.php
@@ -41,13 +41,16 @@ class DoesNotExceedLimitRule implements VacationRequestRule
 
     protected function getUserVacationLimit(User $user, YearPeriod $yearPeriod): int
     {
-        return $user->vacationLimits()->where("year_period_id", $yearPeriod->id)->first()->days ?? 0;
+        return $user->vacationLimits()
+                ->whereBelongsTo($yearPeriod)
+                ->first()
+                ->days ?? 0;
     }
 
     protected function getVacationDaysWithLimit(User $user, YearPeriod $yearPeriod): int
     {
         return $user->vacations()
-            ->where("year_period_id", $yearPeriod->id)
+            ->whereBelongsTo($yearPeriod)
             ->whereRelation(
                 "vacationRequest",
                 fn(Builder $query) => $query
diff --git a/app/Eloquent/Models/User.php b/app/Eloquent/Models/User.php
index 3d12fa9..d4f451c 100644
--- a/app/Eloquent/Models/User.php
+++ b/app/Eloquent/Models/User.php
@@ -91,7 +91,7 @@ class User extends Authenticatable
     public function hasVacationLimit(YearPeriod $yearPeriod): bool
     {
         return $this->vacationLimits()
-            ->where("year_period_id", $yearPeriod->id)
+            ->whereBelongsTo($yearPeriod)
             ->whereNotNull("days")
             ->exists();
     }
@@ -113,7 +113,7 @@ class User extends Authenticatable
         return $query->whereRelation(
             "vacationlimits",
             fn(Builder $query) => $query
-                ->where("year_period_id", $yearPeriod->id)
+                ->whereBelongsTo($yearPeriod)
                 ->whereNotNull("days"),
         );
     }
diff --git a/app/Infrastructure/Http/Controllers/Api/CalculateUserUnavailableDaysController.php b/app/Infrastructure/Http/Controllers/Api/CalculateUserUnavailableDaysController.php
index dfa390d..44715f7 100644
--- a/app/Infrastructure/Http/Controllers/Api/CalculateUserUnavailableDaysController.php
+++ b/app/Infrastructure/Http/Controllers/Api/CalculateUserUnavailableDaysController.php
@@ -27,7 +27,7 @@ class CalculateUserUnavailableDaysController extends Controller
 
         $holidays = $yearPeriod->holidays()->pluck("date");
         $vacationDays = $user->vacations()
-            ->where("year_period_id", $yearPeriod->id)
+            ->whereBelongsTo($yearPeriod)
             ->whereRelation(
                 "vacationRequest",
                 fn(Builder $query) => $query->noStates(VacationRequestStatesRetriever::failedStates()),
diff --git a/app/Infrastructure/Http/Controllers/VacationRequestController.php b/app/Infrastructure/Http/Controllers/VacationRequestController.php
index 4f3134e..fd6b711 100644
--- a/app/Infrastructure/Http/Controllers/VacationRequestController.php
+++ b/app/Infrastructure/Http/Controllers/VacationRequestController.php
@@ -40,26 +40,26 @@ class VacationRequestController extends Controller
         $vacationRequests = $request->user()
             ->vacationRequests()
             ->with("vacations")
-            ->where("year_period_id", $yearPeriodRetriever->selected()->id)
+            ->whereBelongsTo($yearPeriodRetriever->selected())
             ->latest()
             ->states(VacationRequestStatesRetriever::filterByStatusGroup($status, $request->user()))
             ->paginate();
 
         $pending = $request->user()
             ->vacationRequests()
-            ->where("year_period_id", $yearPeriodRetriever->selected()->id)
+            ->whereBelongsTo($yearPeriodRetriever->selected())
             ->states(VacationRequestStatesRetriever::pendingStates())
             ->count();
 
         $success = $request->user()
             ->vacationRequests()
-            ->where("year_period_id", $yearPeriodRetriever->selected()->id)
+            ->whereBelongsTo($yearPeriodRetriever->selected())
             ->states(VacationRequestStatesRetriever::successStates())
             ->count();
 
         $failed = $request->user()
             ->vacationRequests()
-            ->where("year_period_id", $yearPeriodRetriever->selected()->id)
+            ->whereBelongsTo($yearPeriodRetriever->selected())
             ->states(VacationRequestStatesRetriever::failedStates())
             ->count();
 
@@ -91,7 +91,7 @@ class VacationRequestController extends Controller
 
         $vacationRequests = VacationRequest::query()
             ->with(["user", "vacations"])
-            ->where("year_period_id", $yearPeriod->id)
+            ->whereBelongsTo($yearPeriod)
             ->when($user !== null, fn(Builder $query) => $query->where("user_id", $user))
             ->when(
                 $status !== null,
@@ -156,7 +156,7 @@ class VacationRequestController extends Controller
         return $pdf->stream();
     }
 
-    public function create(Request $request, YearPeriodRetriever $yearPeriodRetriever): Response
+    public function create(Request $request): Response
     {
         $users = User::query()
             ->orderBy("last_name")