diff --git a/phpstan.neon b/phpstan.neon
index 638ea20a..6de0f7b6 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -6750,11 +6750,6 @@ parameters:
             count: 2
             path: src/Validator/Constraints/TeamValidator.php
 
-        -
-            message: "#^Cannot call method isVisible\\(\\) on App\\\\Entity\\\\Customer\\|null\\.$#"
-            count: 1
-            path: src/Validator/Constraints/TimesheetBasicValidator.php
-
         -
             message: "#^Cannot call method format\\(\\) on DateTime\\|null\\.$#"
             count: 2
diff --git a/src/Entity/Timesheet.php b/src/Entity/Timesheet.php
index 2f6b74fd..ec6ea75f 100644
--- a/src/Entity/Timesheet.php
+++ b/src/Entity/Timesheet.php
@@ -45,6 +45,7 @@ use Symfony\Component\Validator\Constraints as Assert;
 #[Serializer\VirtualProperty('UserAsId', exp: 'object.getUser().getId()', options: [new Serializer\SerializedName('user'), new Serializer\Type(name: 'integer'), new Serializer\Groups(['Not_Expanded'])])]
 #[Serializer\VirtualProperty('TagsAsArray', exp: 'object.getTagsAsArray()', options: [new Serializer\SerializedName('tags'), new Serializer\Type(name: 'array<string>'), new Serializer\Groups(['Default'])])]
 #[Constraints\Timesheet]
+#[Constraints\TimesheetDeactivated]
 class Timesheet implements EntityWithMetaFields, ExportableItem
 {
     /**
diff --git a/src/Validator/Constraints/TimesheetBasic.php b/src/Validator/Constraints/TimesheetBasic.php
index b5fccbf8..8821e093 100644
--- a/src/Validator/Constraints/TimesheetBasic.php
+++ b/src/Validator/Constraints/TimesheetBasic.php
@@ -16,9 +16,6 @@ final class TimesheetBasic extends TimesheetConstraint
     public const MISSING_ACTIVITY_ERROR = 'kimai-timesheet-84';
     public const MISSING_PROJECT_ERROR = 'kimai-timesheet-85';
     public const ACTIVITY_PROJECT_MISMATCH_ERROR = 'kimai-timesheet-86';
-    public const DISABLED_ACTIVITY_ERROR = 'kimai-timesheet-87';
-    public const DISABLED_PROJECT_ERROR = 'kimai-timesheet-88';
-    public const DISABLED_CUSTOMER_ERROR = 'kimai-timesheet-89';
     public const PROJECT_NOT_STARTED = 'kimai-timesheet-91';
     public const PROJECT_ALREADY_ENDED = 'kimai-timesheet-92';
     public const PROJECT_DISALLOWS_GLOBAL_ACTIVITY = 'kimai-timesheet-93';
@@ -29,9 +26,6 @@ final class TimesheetBasic extends TimesheetConstraint
         self::MISSING_ACTIVITY_ERROR => 'An activity needs to be selected.',
         self::MISSING_PROJECT_ERROR => 'A project needs to be selected.',
         self::ACTIVITY_PROJECT_MISMATCH_ERROR => 'Project mismatch, project specific activity and timesheet project are different.',
-        self::DISABLED_ACTIVITY_ERROR => 'Cannot start a disabled activity.',
-        self::DISABLED_PROJECT_ERROR => 'Cannot start a disabled project.',
-        self::DISABLED_CUSTOMER_ERROR => 'Cannot start a disabled customer.',
         self::PROJECT_NOT_STARTED => 'The project has not started at that time.',
         self::PROJECT_ALREADY_ENDED => 'The project is finished at that time.',
         self::PROJECT_DISALLOWS_GLOBAL_ACTIVITY => 'Global activities are forbidden for the selected project.',
diff --git a/src/Validator/Constraints/TimesheetBasicValidator.php b/src/Validator/Constraints/TimesheetBasicValidator.php
index ffeb0afc..199ac84e 100644
--- a/src/Validator/Constraints/TimesheetBasicValidator.php
+++ b/src/Validator/Constraints/TimesheetBasicValidator.php
@@ -102,33 +102,6 @@ final class TimesheetBasicValidator extends ConstraintValidator
                 ->addViolation();
         }
 
-        $timesheetEnd = $timesheet->getEnd();
-        $newOrStarted = null === $timesheetEnd || $timesheet->getId() === null;
-
-        if ($newOrStarted && $hasActivity && !$activity->isVisible()) {
-            $context->buildViolation(TimesheetBasic::getErrorName(TimesheetBasic::DISABLED_ACTIVITY_ERROR))
-                ->atPath('activity')
-                ->setTranslationDomain('validators')
-                ->setCode(TimesheetBasic::DISABLED_ACTIVITY_ERROR)
-                ->addViolation();
-        }
-
-        if ($newOrStarted && !$project->isVisible()) {
-            $context->buildViolation(TimesheetBasic::getErrorName(TimesheetBasic::DISABLED_PROJECT_ERROR))
-                ->atPath('project')
-                ->setTranslationDomain('validators')
-                ->setCode(TimesheetBasic::DISABLED_PROJECT_ERROR)
-                ->addViolation();
-        }
-
-        if ($newOrStarted && !$project->getCustomer()->isVisible()) {
-            $context->buildViolation(TimesheetBasic::getErrorName(TimesheetBasic::DISABLED_CUSTOMER_ERROR))
-                ->atPath('customer')
-                ->setTranslationDomain('validators')
-                ->setCode(TimesheetBasic::DISABLED_CUSTOMER_ERROR)
-                ->addViolation();
-        }
-
         if ($hasActivity && !$project->isGlobalActivities() && $activity->isGlobal()) {
             $context->buildViolation(TimesheetBasic::getErrorName(TimesheetBasic::PROJECT_DISALLOWS_GLOBAL_ACTIVITY))
                 ->atPath('activity')
diff --git a/src/Validator/Constraints/TimesheetDeactivated.php b/src/Validator/Constraints/TimesheetDeactivated.php
new file mode 100644
index 00000000..7fbdc714
--- /dev/null
+++ b/src/Validator/Constraints/TimesheetDeactivated.php
@@ -0,0 +1,33 @@
+<?php
+
+/*
+ * This file is part of the Kimai time-tracking app.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace App\Validator\Constraints;
+
+use Symfony\Component\Validator\Constraint;
+
+#[\Attribute(\Attribute::TARGET_CLASS)]
+final class TimesheetDeactivated extends Constraint
+{
+    public const DISABLED_ACTIVITY_ERROR = 'kimai-timesheet-deactivated-activity';
+    public const DISABLED_PROJECT_ERROR = 'kimai-timesheet-deactivated-project';
+    public const DISABLED_CUSTOMER_ERROR = 'kimai-timesheet-deactivated-customer';
+
+    protected const ERROR_NAMES = [
+        self::DISABLED_ACTIVITY_ERROR => 'Cannot start a disabled activity.',
+        self::DISABLED_PROJECT_ERROR => 'Cannot start a disabled project.',
+        self::DISABLED_CUSTOMER_ERROR => 'Cannot start a disabled customer.',
+    ];
+
+    public string $message = 'This timesheet has invalid settings.';
+
+    public function getTargets(): string|array
+    {
+        return self::CLASS_CONSTRAINT;
+    }
+}
diff --git a/src/Validator/Constraints/TimesheetDeactivatedValidator.php b/src/Validator/Constraints/TimesheetDeactivatedValidator.php
new file mode 100644
index 00000000..574c3380
--- /dev/null
+++ b/src/Validator/Constraints/TimesheetDeactivatedValidator.php
@@ -0,0 +1,84 @@
+<?php
+
+/*
+ * This file is part of the Kimai time-tracking app.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace App\Validator\Constraints;
+
+use App\Entity\Timesheet as TimesheetEntity;
+use Symfony\Component\Validator\Constraint;
+use Symfony\Component\Validator\ConstraintValidator;
+use Symfony\Component\Validator\Context\ExecutionContextInterface;
+use Symfony\Component\Validator\Exception\UnexpectedTypeException;
+
+/**
+ * This validator is separate, so it can be easily deactivated in import scenarios.
+ */
+final class TimesheetDeactivatedValidator extends ConstraintValidator
+{
+    public function validate(mixed $value, Constraint $constraint): void
+    {
+        if (!($constraint instanceof TimesheetDeactivated)) {
+            throw new UnexpectedTypeException($constraint, TimesheetDeactivated::class);
+        }
+
+        if (!\is_object($value) || !($value instanceof TimesheetEntity)) {
+            throw new UnexpectedTypeException($value, TimesheetEntity::class);
+        }
+
+        $this->validateActivityAndProject($value, $this->context);
+    }
+
+    /**
+     * @param TimesheetEntity $timesheet
+     * @param ExecutionContextInterface $context
+     */
+    protected function validateActivityAndProject(TimesheetEntity $timesheet, ExecutionContextInterface $context): void
+    {
+        $timesheetEnd = $timesheet->getEnd();
+        $newOrStarted = null === $timesheetEnd || $timesheet->getId() === null;
+
+        if (!$newOrStarted) {
+            return;
+        }
+
+        $activity = $timesheet->getActivity();
+        if (null !== $activity && !$activity->isVisible()) {
+            $context->buildViolation(TimesheetDeactivated::getErrorName(TimesheetDeactivated::DISABLED_ACTIVITY_ERROR))
+                ->atPath('activity')
+                ->setTranslationDomain('validators')
+                ->setCode(TimesheetDeactivated::DISABLED_ACTIVITY_ERROR)
+                ->addViolation();
+        }
+
+        $project = $timesheet->getProject();
+        if ($project === null) {
+            return;
+        }
+
+        if (!$project->isVisible()) {
+            $context->buildViolation(TimesheetDeactivated::getErrorName(TimesheetDeactivated::DISABLED_PROJECT_ERROR))
+                ->atPath('project')
+                ->setTranslationDomain('validators')
+                ->setCode(TimesheetDeactivated::DISABLED_PROJECT_ERROR)
+                ->addViolation();
+        }
+
+        $customer = $project->getCustomer();
+        if ($customer === null) {
+            return;
+        }
+
+        if (!$customer->isVisible()) {
+            $context->buildViolation(TimesheetDeactivated::getErrorName(TimesheetDeactivated::DISABLED_CUSTOMER_ERROR))
+                ->atPath('customer')
+                ->setTranslationDomain('validators')
+                ->setCode(TimesheetDeactivated::DISABLED_CUSTOMER_ERROR)
+                ->addViolation();
+        }
+    }
+}
diff --git a/src/Validator/Constraints/TimesheetValidator.php b/src/Validator/Constraints/TimesheetValidator.php
index 172e2966..a76b114b 100644
--- a/src/Validator/Constraints/TimesheetValidator.php
+++ b/src/Validator/Constraints/TimesheetValidator.php
@@ -38,11 +38,16 @@ final class TimesheetValidator extends ConstraintValidator
             throw new UnexpectedTypeException($timesheet, TimesheetEntity::class);
         }
 
+        $groups = [Constraint::DEFAULT_GROUP];
+        if ($this->context->getGroup() !== null) {
+            $groups = [$this->context->getGroup()];
+        }
+
         foreach ($this->constraints as $innerConstraint) {
             $this->context
                 ->getValidator()
                 ->inContext($this->context)
-                ->validate($timesheet, $innerConstraint, [Constraint::DEFAULT_GROUP]);
+                ->validate($timesheet, $innerConstraint, $groups);
         }
     }
 }
diff --git a/tests/Entity/TimesheetValidationTest.php b/tests/Entity/TimesheetValidationTest.php
index dd3685f5..ef19d2e9 100644
--- a/tests/Entity/TimesheetValidationTest.php
+++ b/tests/Entity/TimesheetValidationTest.php
@@ -99,6 +99,7 @@ class TimesheetValidationTest extends KernelTestCase
         $entity->setActivity($activity);
         $entity->setProject($project);
         $entity->setBegin(new \DateTime());
+        $entity->setEnd(new \DateTime());
 
         $this->assertHasViolationForField($entity, 'customer');
     }
@@ -166,6 +167,7 @@ class TimesheetValidationTest extends KernelTestCase
         $entity->setActivity($activity);
         $entity->setProject($project);
         $entity->setBegin(new \DateTime());
+        $entity->setEnd(new \DateTime());
 
         $this->assertHasViolationForField($entity, 'project');
     }
@@ -203,6 +205,7 @@ class TimesheetValidationTest extends KernelTestCase
         $entity->setActivity($activity);
         $entity->setProject($project);
         $entity->setBegin(new \DateTime());
+        $entity->setEnd(new \DateTime());
 
         $this->assertHasViolationForField($entity, 'activity');
     }
diff --git a/tests/Validator/Constraints/TimesheetBasicValidatorTest.php b/tests/Validator/Constraints/TimesheetBasicValidatorTest.php
index e411e950..0b3bcc49 100644
--- a/tests/Validator/Constraints/TimesheetBasicValidatorTest.php
+++ b/tests/Validator/Constraints/TimesheetBasicValidatorTest.php
@@ -143,39 +143,6 @@ class TimesheetBasicValidatorTest extends ConstraintValidatorTestCase
             ->assertRaised();
     }
 
-    public function testDisabledValuesDuringStart()
-    {
-        $begin = new \DateTime('-10 hour');
-        $customer = new Customer('foo');
-        $customer->setVisible(false);
-        $activity = new Activity();
-        $activity->setVisible(false);
-        $project = new Project();
-        $project->setVisible(false);
-        $project->setCustomer($customer);
-        $activity->setProject($project);
-
-        $timesheet = new Timesheet();
-        $timesheet
-            ->setBegin($begin)
-            ->setActivity($activity)
-            ->setProject($project)
-        ;
-
-        $this->validator->validate($timesheet, new TimesheetBasic(['message' => 'myMessage']));
-
-        $this->buildViolation('Cannot start a disabled activity.')
-            ->atPath('property.path.activity')
-            ->setCode(TimesheetBasic::DISABLED_ACTIVITY_ERROR)
-            ->buildNextViolation('Cannot start a disabled project.')
-            ->atPath('property.path.project')
-            ->setCode(TimesheetBasic::DISABLED_PROJECT_ERROR)
-            ->buildNextViolation('Cannot start a disabled customer.')
-            ->atPath('property.path.customer')
-            ->setCode(TimesheetBasic::DISABLED_CUSTOMER_ERROR)
-            ->assertRaised();
-    }
-
     public function getProjectStartEndTestData()
     {
         yield [new \DateTime(), new \DateTime(), [
diff --git a/tests/Validator/Constraints/TimesheetDeactivatedValidatorTest.php b/tests/Validator/Constraints/TimesheetDeactivatedValidatorTest.php
new file mode 100644
index 00000000..47ab05c7
--- /dev/null
+++ b/tests/Validator/Constraints/TimesheetDeactivatedValidatorTest.php
@@ -0,0 +1,86 @@
+<?php
+
+/*
+ * This file is part of the Kimai time-tracking app.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace App\Tests\Validator\Constraints;
+
+use App\Entity\Activity;
+use App\Entity\Customer;
+use App\Entity\Project;
+use App\Entity\Timesheet;
+use App\Validator\Constraints\TimesheetDeactivated;
+use App\Validator\Constraints\TimesheetDeactivatedValidator;
+use Symfony\Component\Validator\Constraints\NotBlank;
+use Symfony\Component\Validator\Exception\UnexpectedTypeException;
+use Symfony\Component\Validator\Test\ConstraintValidatorTestCase;
+
+/**
+ * @covers \App\Validator\Constraints\TimesheetDeactivated
+ * @covers \App\Validator\Constraints\TimesheetDeactivatedValidator
+ * @extends ConstraintValidatorTestCase<TimesheetDeactivatedValidator>
+ */
+class TimesheetDeactivatedValidatorTest extends ConstraintValidatorTestCase
+{
+    protected function createValidator(): TimesheetDeactivatedValidator
+    {
+        return new TimesheetDeactivatedValidator();
+    }
+
+    public function testConstraintIsInvalid(): void
+    {
+        $this->expectException(UnexpectedTypeException::class);
+
+        $this->validator->validate(new Timesheet(), new NotBlank());
+    }
+
+    public function testInvalidValueThrowsException(): void
+    {
+        $this->expectException(UnexpectedTypeException::class);
+
+        $this->validator->validate(new NotBlank(), new TimesheetDeactivated(['message' => 'myMessage']));
+    }
+
+    public function testDisabledValuesDuringStart(): void
+    {
+        $begin = new \DateTime('-10 hour');
+        $customer = new Customer('foo');
+        $customer->setVisible(false);
+        $activity = new Activity();
+        $activity->setVisible(false);
+        $project = new Project();
+        $project->setVisible(false);
+        $project->setCustomer($customer);
+        $activity->setProject($project);
+
+        $timesheet = new Timesheet();
+        $timesheet
+            ->setBegin($begin)
+            ->setActivity($activity)
+            ->setProject($project)
+        ;
+
+        $this->validator->validate($timesheet, new TimesheetDeactivated(['message' => 'myMessage']));
+
+        $this->buildViolation(TimesheetDeactivated::getErrorName(TimesheetDeactivated::DISABLED_ACTIVITY_ERROR))
+            ->atPath('property.path.activity')
+            ->setCode(TimesheetDeactivated::DISABLED_ACTIVITY_ERROR)
+            ->buildNextViolation(TimesheetDeactivated::getErrorName(TimesheetDeactivated::DISABLED_PROJECT_ERROR))
+            ->atPath('property.path.project')
+            ->setCode(TimesheetDeactivated::DISABLED_PROJECT_ERROR)
+            ->buildNextViolation(TimesheetDeactivated::getErrorName(TimesheetDeactivated::DISABLED_CUSTOMER_ERROR))
+            ->atPath('property.path.customer')
+            ->setCode(TimesheetDeactivated::DISABLED_CUSTOMER_ERROR)
+            ->assertRaised();
+    }
+
+    public function testGetTargets(): void
+    {
+        $constraint = new TimesheetDeactivated();
+        self::assertEquals('class', $constraint->getTargets());
+    }
+}
diff --git a/tests/phpstan.neon b/tests/phpstan.neon
index e1f48bf9..8f98348b 100644
--- a/tests/phpstan.neon
+++ b/tests/phpstan.neon
@@ -10522,11 +10522,6 @@ parameters:
             count: 1
             path: Validator/Constraints/TimesheetBasicValidatorTest.php
 
-        -
-            message: "#^Method App\\\\Tests\\\\Validator\\\\Constraints\\\\TimesheetBasicValidatorTest\\:\\:testDisabledValuesDuringStart\\(\\) has no return type specified\\.$#"
-            count: 1
-            path: Validator/Constraints/TimesheetBasicValidatorTest.php
-
         -
             message: "#^Method App\\\\Tests\\\\Validator\\\\Constraints\\\\TimesheetBasicValidatorTest\\:\\:testEmptyTimesheet\\(\\) has no return type specified\\.$#"
             count: 1