diff --git a/.idea/composerJson.xml b/.idea/composerJson.xml
new file mode 100644
index 0000000..1b07430
--- /dev/null
+++ b/.idea/composerJson.xml
@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ComposerJsonPluginSettings">
+    <unboundedVersionInspectionSettings>
+      <excludedPackages />
+    </unboundedVersionInspectionSettings>
+    <customRepositories />
+    <composerUpdateOptions />
+  </component>
+</project>
\ No newline at end of file
diff --git a/src/UCRM/REST/Endpoints/Endpoint.php b/src/UCRM/REST/Endpoints/Endpoint.php
index b582675..27d71f4 100644
--- a/src/UCRM/REST/Endpoints/Endpoint.php
+++ b/src/UCRM/REST/Endpoints/Endpoint.php
@@ -43,6 +43,7 @@ public function getId(): int
     /**
      * @param string $override
      * @param array $params
+     * @param array $query
      * @return Collection
      * @throws AnnotationReaderException
      * @throws CollectionException
@@ -52,7 +53,7 @@ public function getId(): int
      * @throws \MVQN\Helpers\Exceptions\ArrayHelperException
      * @throws \ReflectionException
      */
-    public static function get(string $override = "", array $params = []): Collection
+    public static function get(string $override = "", array $params = [], array $query = []): Collection
     {
         // Get a reference to the type of Endpoint calling this function.
         $class = get_called_class();
@@ -84,6 +85,17 @@ public static function get(string $override = "", array $params = []): Collectio
             //$endpoint = $override;
         }
 
+        // Appen any provided suffixes to the URL (i.e. query string).
+        if($query !== [])
+        {
+            $pairs = [];
+
+            foreach($query as $key => $value)
+                $pairs[] = "$key=$value";
+
+            $endpoint .= "?".implode("&", $pairs);
+        }
+
         // Attempt to GET the specified Endpoint.
         $response = RestClient::get($endpoint);
 
diff --git a/src/UCRM/REST/Endpoints/Helpers/InvoiceHelper.php b/src/UCRM/REST/Endpoints/Helpers/InvoiceHelper.php
index 3fec33c..5600b3e 100644
--- a/src/UCRM/REST/Endpoints/Helpers/InvoiceHelper.php
+++ b/src/UCRM/REST/Endpoints/Helpers/InvoiceHelper.php
@@ -12,7 +12,7 @@
 use UCRM\REST\Exceptions\RestClientException;
 use UCRM\REST\Exceptions\RestObjectException;
 
-use UCRM\REST\Endpoints\{Client, Invoice};
+use UCRM\REST\Endpoints\{Client, Collections\ClientCollection, Collections\InvoiceCollection, Invoice};
 use UCRM\REST\Endpoints\Lookups\InvoiceItem;
 
 
@@ -69,6 +69,40 @@ public function update(): Invoice
         return $invoice;
     }
 
+    // =================================================================================================================
+    // READ FUNCTIONS
+    // -----------------------------------------------------------------------------------------------------------------
+
+    public static function getByClientId(int $clientId): InvoiceCollection
+    {
+        /** @var InvoiceCollection $invoices */
+        $invoices = Invoice::get("", [], [ "clientId" => $clientId ]);
+
+        return new InvoiceCollection($invoices->elements());
+    }
+
+    public static function getByCreatedDate(\DateTime $date): InvoiceCollection
+    {
+        /** @var InvoiceCollection $invoices */
+        $invoices = Invoice::get("", [], [ "createdDateFrom" => $date->format("Y-m-d"),
+            "createdDateTo" => $date->format("Y-m-d") ]);
+
+        return new InvoiceCollection($invoices->elements());
+    }
+
+    public static function getByCreatedDateBetween(\DateTime $from, \DateTime $to): InvoiceCollection
+    {
+        /** @var InvoiceCollection $invoices */
+        $invoices = Invoice::get("", [], [ "createdDateFrom" => $from->format("Y-m-d"),
+            "createdDateTo" => $to->format("Y-m-d") ]);
+
+        return new InvoiceCollection($invoices->elements());
+    }
+
+    // TODO: Add more helpers for the remaining query parameters!
+
+
+
     // =================================================================================================================
     // EXTRA FUNCTIONS
     // -----------------------------------------------------------------------------------------------------------------
diff --git a/tests/UCRM/REST/Endpoints/_02_ClientTests.php b/tests/UCRM/REST/Endpoints/_02_ClientTests.php
index 67d64aa..916ca45 100644
--- a/tests/UCRM/REST/Endpoints/_02_ClientTests.php
+++ b/tests/UCRM/REST/Endpoints/_02_ClientTests.php
@@ -256,7 +256,6 @@ public function testGetById()
     }
 
 
-
     // =================================================================================================================
     // UPDATE METHODS
     // -----------------------------------------------------------------------------------------------------------------
diff --git a/tests/UCRM/REST/Endpoints/_12_InvoiceTests.php b/tests/UCRM/REST/Endpoints/_12_InvoiceTests.php
index 10c5dee..94a08b2 100644
--- a/tests/UCRM/REST/Endpoints/_12_InvoiceTests.php
+++ b/tests/UCRM/REST/Endpoints/_12_InvoiceTests.php
@@ -64,6 +64,24 @@ public function testGetById()
         echo $invoice."\n";
     }
 
+
+    public function testGetByClientId()
+    {
+        $invoices = Invoice::getByClientId(1);
+        $this->assertNotNull($invoices);
+
+        echo ">>> Invoice::getByClientId(1)\n";
+        echo $invoices."\n";
+        echo "\n";
+    }
+
+
+
+
+
+
+
+
     public function testAddInvoiceItem()
     {
         $this->markTestSkipped("Each addition duplicates all other line items as well; waiting on info from UBNT!");