diff --git a/src/GooglePlay/Acknowledger.php b/src/GooglePlay/Acknowledger.php
index bd9b166..c464b92 100644
--- a/src/GooglePlay/Acknowledger.php
+++ b/src/GooglePlay/Acknowledger.php
@@ -2,16 +2,25 @@
 
 namespace ReceiptValidator\GooglePlay;
 
+use Exception;
+use Google_Service_AndroidPublisher;
+use ReceiptValidator\RunTimeException;
+
 /**
  * Class Acknowledger.
  */
 class Acknowledger
 {
+    // Do acknowledge only in case if it have not done
+    const ACKNOWLEDGE_STRATEGY_IMPLICIT = 'strategy_implicit';
+    // Try to do acknowledge directly (exception will be returned in case when acknowledge already was done)
+    const ACKNOWLEDGE_STRATEGY_EXPLICIT = 'strategy_explicit';
+
     const SUBSCRIPTION = 'SUBSCRIPTION';
     const PRODUCT = 'PRODUCT';
 
     /**
-     * @var \Google_Service_AndroidPublisher
+     * @var Google_Service_AndroidPublisher
      */
     protected $androidPublisherService;
     /**
@@ -26,31 +35,46 @@ class Acknowledger
      * @var string
      */
     protected $productId;
+    /**
+     * @var string
+     */
+    protected $strategy;
 
     /**
      * Acknowledger constructor.
      *
-     * @param \Google_Service_AndroidPublisher $googleServiceAndroidPublisher
-     * @param string                           $packageName
-     * @param string                           $purchaseToken
-     * @param string                           $productId
+     * @param Google_Service_AndroidPublisher $googleServiceAndroidPublisher
+     * @param string                          $packageName
+     * @param string                          $purchaseToken
+     * @param string                          $productId
+     * @param string                          $strategy
+     *
+     * @throws RunTimeException
      */
     public function __construct(
-        \Google_Service_AndroidPublisher $googleServiceAndroidPublisher,
+        Google_Service_AndroidPublisher $googleServiceAndroidPublisher,
         $packageName,
         $productId,
-        $purchaseToken
+        $purchaseToken,
+        $strategy = self::ACKNOWLEDGE_STRATEGY_EXPLICIT
     ) {
+        if (!in_array($strategy, [self::ACKNOWLEDGE_STRATEGY_EXPLICIT, self::ACKNOWLEDGE_STRATEGY_IMPLICIT])) {
+            throw new RuntimeException(sprintf('Invalid strategy provided %s', $strategy));
+        }
+
         $this->androidPublisherService = $googleServiceAndroidPublisher;
         $this->packageName = $packageName;
         $this->purchaseToken = $purchaseToken;
         $this->productId = $productId;
+        $this->strategy = $strategy;
     }
 
     /**
      * @param string $type
      * @param string $developerPayload
      *
+     * @throws RunTimeException
+     *
      * @return bool
      */
     public function acknowledge(string $type = self::SUBSCRIPTION, string $developerPayload = '')
@@ -58,28 +82,68 @@ public function acknowledge(string $type = self::SUBSCRIPTION, string $developer
         try {
             switch ($type) {
                 case self::SUBSCRIPTION:
-                    $this->androidPublisherService->purchases_subscriptions->acknowledge(
-                        $this->packageName,
-                        $this->productId,
-                        $this->purchaseToken,
-                        new \Google_Service_AndroidPublisher_SubscriptionPurchasesAcknowledgeRequest(
-                            ['developerPayload' => $developerPayload]
-                        )
-                    );
+                    if ($this->strategy === self::ACKNOWLEDGE_STRATEGY_EXPLICIT) {
+                        // Here exception might be thrown as previously, so no BC break here
+                        $this->androidPublisherService->purchases_subscriptions->acknowledge(
+                            $this->packageName,
+                            $this->productId,
+                            $this->purchaseToken,
+                            new \Google_Service_AndroidPublisher_SubscriptionPurchasesAcknowledgeRequest(
+                                ['developerPayload' => $developerPayload]
+                            )
+                        );
+                    } elseif ($this->strategy === self::ACKNOWLEDGE_STRATEGY_IMPLICIT) {
+                        $subscriptionPurchase = $this->androidPublisherService->purchases_subscriptions->get(
+                            $this->packageName,
+                            $this->productId,
+                            $this->purchaseToken
+                        );
+
+                        if ($subscriptionPurchase->getAcknowledgementState() !== AbstractResponse::ACKNOWLEDGEMENT_STATE_DONE) {
+                            $this->androidPublisherService->purchases_subscriptions->acknowledge(
+                                $this->packageName,
+                                $this->productId,
+                                $this->purchaseToken,
+                                new \Google_Service_AndroidPublisher_SubscriptionPurchasesAcknowledgeRequest(
+                                    ['developerPayload' => $developerPayload]
+                                )
+                            );
+                        }
+                    }
                     break;
                 case self::PRODUCT:
-                    $this->androidPublisherService->purchases_products->acknowledge(
-                        $this->packageName,
-                        $this->productId,
-                        $this->purchaseToken,
-                        new \Google_Service_AndroidPublisher_ProductPurchasesAcknowledgeRequest(
-                            ['developerPayload' => $developerPayload]
-                        )
-                    );
+                    if ($this->strategy === self::ACKNOWLEDGE_STRATEGY_EXPLICIT) {
+                        // Here exception might be thrown as previously, so no BC break here
+                        $this->androidPublisherService->purchases_products->acknowledge(
+                            $this->packageName,
+                            $this->productId,
+                            $this->purchaseToken,
+                            new \Google_Service_AndroidPublisher_ProductPurchasesAcknowledgeRequest(
+                                ['developerPayload' => $developerPayload]
+                            )
+                        );
+                    } elseif ($this->strategy === self::ACKNOWLEDGE_STRATEGY_IMPLICIT) {
+                        $productPurchase = $this->androidPublisherService->purchases_products->get(
+                            $this->packageName,
+                            $this->productId,
+                            $this->purchaseToken
+                        );
+
+                        if ($productPurchase->getAcknowledgementState() !== AbstractResponse::ACKNOWLEDGEMENT_STATE_DONE) {
+                            $this->androidPublisherService->purchases_products->acknowledge(
+                                $this->packageName,
+                                $this->productId,
+                                $this->purchaseToken,
+                                new \Google_Service_AndroidPublisher_ProductPurchasesAcknowledgeRequest(
+                                    ['developerPayload' => $developerPayload]
+                                )
+                            );
+                        }
+                    }
                     break;
                 default:
                     throw new \RuntimeException(
-                        \sprintf(
+                        sprintf(
                             'Invalid type provided : %s expected %s',
                             $type,
                             implode(',', [self::PRODUCT, self::SUBSCRIPTION])
@@ -88,8 +152,8 @@ public function acknowledge(string $type = self::SUBSCRIPTION, string $developer
             }
 
             return true;
-        } catch (\Exception $e) {
-            throw new \RuntimeException($e->getMessage(), $e->getCode(), $e);
+        } catch (Exception $e) {
+            throw new \RuntimeException($e->getCode(), $e->getCode(), $e);
         }
     }
 }
diff --git a/tests/GooglePlay/GooglePlayAcknowledgerTest.php b/tests/GooglePlay/GooglePlayAcknowledgerTest.php
index 6a4eda7..f5d10b0 100755
--- a/tests/GooglePlay/GooglePlayAcknowledgerTest.php
+++ b/tests/GooglePlay/GooglePlayAcknowledgerTest.php
@@ -3,8 +3,10 @@
 namespace ReceiptValidator\Tests;
 
 use Google_Service_AndroidPublisher;
+use Google_Service_AndroidPublisher_ProductPurchase;
 use Google_Service_AndroidPublisher_Resource_PurchasesProducts;
 use Google_Service_AndroidPublisher_Resource_PurchasesSubscriptions;
+use Google_Service_AndroidPublisher_SubscriptionPurchase;
 use PHPUnit\Framework\TestCase;
 use ReceiptValidator\GooglePlay\Acknowledger;
 
@@ -13,7 +15,7 @@
  */
 class GooglePlayAcknowledgerTest extends TestCase
 {
-    public function testValidate(): void
+    public function testValidateWithNonAcknowledgedPurchase(): void
     {
         $packageName = 'testPackage';
         $productId = '15';
@@ -21,35 +23,221 @@ public function testValidate(): void
 
         // mock objects
         $googleServiceAndroidPublisherMock = $this->getMockBuilder(Google_Service_AndroidPublisher::class)
-            ->disableOriginalConstructor()->getMock();
-        $productPurchaseMock = $this->getMockBuilder(Google_Service_AndroidPublisher_Resource_PurchasesProducts::class)
-            ->disableOriginalConstructor()->getMock();
-        $subscriptionPurchaseMock = $this->getMockBuilder(Google_Service_AndroidPublisher_Resource_PurchasesSubscriptions::class)
-            ->disableOriginalConstructor()->getMock();
+                                                  ->disableOriginalConstructor()->getMock();
+
+        // products
+        $purchasesProductsMock = $this->getMockBuilder(
+            Google_Service_AndroidPublisher_Resource_PurchasesProducts::class
+        )
+                                      ->disableOriginalConstructor()->getMock();
+        $productPurchaseMock = $this->getMockBuilder(Google_Service_AndroidPublisher_ProductPurchase::class)
+                                    ->disableOriginalConstructor()->getMock();
+        $productPurchaseMock->expects($this->any())->method('getAcknowledgementState')->willReturn(0);
+
+        // subscriptions
+        $purchasesSubscriptionsMock = $this->getMockBuilder(
+            Google_Service_AndroidPublisher_Resource_PurchasesSubscriptions::class
+        )
+                                           ->disableOriginalConstructor()->getMock();
+        $subscriptionPurchaseMock = $this->getMockBuilder(Google_Service_AndroidPublisher_SubscriptionPurchase::class)
+                                         ->disableOriginalConstructor()->getMock();
+        $subscriptionPurchaseMock->expects($this->any())->method('getAcknowledgementState')->willReturn(0);
+
+        // mock expectations
+        $googleServiceAndroidPublisherMock->purchases_products = $purchasesProductsMock;
+        $googleServiceAndroidPublisherMock->purchases_subscriptions = $purchasesSubscriptionsMock;
+
+        $purchasesProductsMock->expects($this->once())->method('acknowledge')
+                              ->with(
+                                  $packageName,
+                                  $productId,
+                                  $purchaseToken,
+                                  new \Google_Service_AndroidPublisher_ProductPurchasesAcknowledgeRequest(
+                                      ['developerPayload' => 'bar']
+                                  )
+                              );
+
+        $purchasesSubscriptionsMock->expects($this->once())->method('acknowledge')
+                                   ->with(
+                                       $packageName,
+                                       $productId,
+                                       $purchaseToken,
+                                       new \Google_Service_AndroidPublisher_SubscriptionPurchasesAcknowledgeRequest(
+                                           ['developerPayload' => 'foo']
+                                       )
+                                   );
+
+        $googlePlayAcknowledger = new Acknowledger(
+            $googleServiceAndroidPublisherMock,
+            $packageName,
+            $productId,
+            $purchaseToken
+        );
+
+        $googlePlayAcknowledger->acknowledge(Acknowledger::SUBSCRIPTION, 'foo');
+        $googlePlayAcknowledger->acknowledge(Acknowledger::PRODUCT, 'bar');
+    }
+
+    public function testValidateWithAcknowledgedPurchaseAndImplicitStrategy(): void
+    {
+        $packageName = 'testPackage';
+        $productId = '15';
+        $purchaseToken = 'testPurchaseToken';
+
+        // mock objects
+        $googleServiceAndroidPublisherMock = $this->getMockBuilder(Google_Service_AndroidPublisher::class)
+                                                  ->disableOriginalConstructor()->getMock();
+
+        // products
+        $purchasesProductsMock = $this->getMockBuilder(
+            Google_Service_AndroidPublisher_Resource_PurchasesProducts::class
+        )
+                                      ->disableOriginalConstructor()->getMock();
+        $productPurchaseMock = $this->getMockBuilder(Google_Service_AndroidPublisher_ProductPurchase::class)
+                                    ->disableOriginalConstructor()->getMock();
+        $productPurchaseMock->expects($this->any())->method('getAcknowledgementState')->willReturn(1);
+
+        // subscriptions
+        $purchasesSubscriptionsMock = $this->getMockBuilder(
+            Google_Service_AndroidPublisher_Resource_PurchasesSubscriptions::class
+        )
+                                           ->disableOriginalConstructor()->getMock();
+        $subscriptionPurchaseMock = $this->getMockBuilder(Google_Service_AndroidPublisher_SubscriptionPurchase::class)
+                                         ->disableOriginalConstructor()->getMock();
+        $subscriptionPurchaseMock->expects($this->any())->method('getAcknowledgementState')->willReturn(1);
+
+        // mock expectations
+        $googleServiceAndroidPublisherMock->purchases_products = $purchasesProductsMock;
+        $googleServiceAndroidPublisherMock->purchases_subscriptions = $purchasesSubscriptionsMock;
+
+        $purchasesProductsMock->expects($this->once())->method('get')
+                              ->with(
+                                  $packageName,
+                                  $productId,
+                                  $purchaseToken
+                              )->willReturn($productPurchaseMock);
+        $purchasesProductsMock->expects($this->never())->method('acknowledge')
+                              ->with(
+                                  $packageName,
+                                  $productId,
+                                  $purchaseToken,
+                                  new \Google_Service_AndroidPublisher_ProductPurchasesAcknowledgeRequest(
+                                      ['developerPayload' => 'bar']
+                                  )
+                              );
+
+        $purchasesSubscriptionsMock->expects($this->once())->method('get')
+                                   ->with(
+                                       $packageName,
+                                       $productId,
+                                       $purchaseToken
+                                   )->willReturn($subscriptionPurchaseMock);
+        $purchasesSubscriptionsMock->expects($this->never())->method('acknowledge')
+                                   ->with(
+                                       $packageName,
+                                       $productId,
+                                       $purchaseToken,
+                                       new \Google_Service_AndroidPublisher_SubscriptionPurchasesAcknowledgeRequest(
+                                           ['developerPayload' => 'foo']
+                                       )
+                                   );
+
+        $googlePlayAcknowledger = new Acknowledger(
+            $googleServiceAndroidPublisherMock,
+            $packageName,
+            $productId,
+            $purchaseToken,
+            Acknowledger::ACKNOWLEDGE_STRATEGY_IMPLICIT
+        );
+
+        $googlePlayAcknowledger->acknowledge(Acknowledger::SUBSCRIPTION, 'foo');
+        $googlePlayAcknowledger->acknowledge(Acknowledger::PRODUCT, 'bar');
+    }
+
+    public function testValidateWithAcknowledgedPurchaseAndExplicitStrategyForSubscription(): void
+    {
+        $packageName = 'testPackage';
+        $productId = '15';
+        $purchaseToken = 'testPurchaseToken';
+
+        // mock objects
+        $googleServiceAndroidPublisherMock = $this->getMockBuilder(Google_Service_AndroidPublisher::class)
+                                                  ->disableOriginalConstructor()
+                                                  ->getMock();
+
+        // subscriptions
+        $purchasesSubscriptionsMock = $this->getMockBuilder(
+            Google_Service_AndroidPublisher_Resource_PurchasesSubscriptions::class
+        )
+                                           ->disableOriginalConstructor()
+                                           ->getMock();
+        $subscriptionPurchaseMock = $this->getMockBuilder(Google_Service_AndroidPublisher_SubscriptionPurchase::class)
+                                         ->disableOriginalConstructor()
+                                         ->getMock();
+        $subscriptionPurchaseMock->expects($this->any())->method('getAcknowledgementState')->willReturn(1);
 
         // mock expectations
-        $googleServiceAndroidPublisherMock->purchases_products = $productPurchaseMock;
-        $googleServiceAndroidPublisherMock->purchases_subscriptions = $subscriptionPurchaseMock;
-
-        $productPurchaseMock->expects($this->once())->method('acknowledge')
-            ->with(
-                $packageName,
-                $productId,
-                $purchaseToken,
-                new \Google_Service_AndroidPublisher_ProductPurchasesAcknowledgeRequest(['developerPayload' => 'bar'])
-            );
-
-        $subscriptionPurchaseMock->expects($this->once())->method('acknowledge')
-            ->with(
-                $packageName,
-                $productId,
-                $purchaseToken,
-                new \Google_Service_AndroidPublisher_SubscriptionPurchasesAcknowledgeRequest(['developerPayload' => 'foo'])
-            );
-
-        $googlePlayAcknowledger = new Acknowledger($googleServiceAndroidPublisherMock, $packageName, $productId, $purchaseToken);
+        $googleServiceAndroidPublisherMock->purchases_subscriptions = $purchasesSubscriptionsMock;
+
+        $purchasesSubscriptionsMock->expects($this->once())->method('acknowledge')
+                                   ->with(
+                                       $packageName,
+                                       $productId,
+                                       $purchaseToken,
+                                       new \Google_Service_AndroidPublisher_SubscriptionPurchasesAcknowledgeRequest(
+                                           ['developerPayload' => 'foo']
+                                       )
+                                   );
+
+        $googlePlayAcknowledger = new Acknowledger(
+            $googleServiceAndroidPublisherMock,
+            $packageName,
+            $productId,
+            $purchaseToken
+        );
 
         $googlePlayAcknowledger->acknowledge(Acknowledger::SUBSCRIPTION, 'foo');
+    }
+
+    public function testValidateWithAcknowledgedPurchaseAndExplicitStrategyForProduct(): void
+    {
+        $packageName = 'testPackage';
+        $productId = '15';
+        $purchaseToken = 'testPurchaseToken';
+
+        // mock objects
+        $googleServiceAndroidPublisherMock = $this->getMockBuilder(Google_Service_AndroidPublisher::class)
+                                                  ->disableOriginalConstructor()->getMock();
+
+        // products
+        $purchasesProductsMock = $this->getMockBuilder(
+            Google_Service_AndroidPublisher_Resource_PurchasesProducts::class
+        )
+                                      ->disableOriginalConstructor()->getMock();
+        $productPurchaseMock = $this->getMockBuilder(Google_Service_AndroidPublisher_ProductPurchase::class)
+                                    ->disableOriginalConstructor()->getMock();
+        $productPurchaseMock->expects($this->any())->method('getAcknowledgementState')->willReturn(1);
+
+        // mock expectations
+        $googleServiceAndroidPublisherMock->purchases_products = $purchasesProductsMock;
+
+        $purchasesProductsMock->expects($this->once())->method('acknowledge')
+                              ->with(
+                                  $packageName,
+                                  $productId,
+                                  $purchaseToken,
+                                  new \Google_Service_AndroidPublisher_ProductPurchasesAcknowledgeRequest(
+                                      ['developerPayload' => 'bar']
+                                  )
+                              );
+
+        $googlePlayAcknowledger = new Acknowledger(
+            $googleServiceAndroidPublisherMock,
+            $packageName,
+            $productId,
+            $purchaseToken
+        );
+
         $googlePlayAcknowledger->acknowledge(Acknowledger::PRODUCT, 'bar');
     }
 }