diff --git a/application/models/Service_categories_model.php b/application/models/Service_categories_model.php
new file mode 100644
index 00000000..3641be91
--- /dev/null
+++ b/application/models/Service_categories_model.php
@@ -0,0 +1,259 @@
+<?php defined('BASEPATH') or exit('No direct script access allowed');
+
+/* ----------------------------------------------------------------------------
+ * Easy!Appointments - Open Source Web Scheduler
+ *
+ * @package     EasyAppointments
+ * @author      A.Tselegidis <alextselegidis@gmail.com>
+ * @copyright   Copyright (c) 2013 - 2020, Alex Tselegidis
+ * @license     http://opensource.org/licenses/GPL-3.0 - GPLv3
+ * @link        http://easyappointments.org
+ * @since       v1.0.0
+ * ---------------------------------------------------------------------------- */
+
+/**
+ * Services categories model
+ *
+ * Handles all the database operations of the service category resource.
+ *
+ * @package Models
+ */
+class Service_categories_model extends EA_Model {
+    /**
+     * Save (insert or update) a service category.
+     *
+     * @param array $service_category Associative array with the service category data.
+     *
+     * @return int Returns the service category ID.
+     *
+     * @throws InvalidArgumentException
+     */
+    public function save(array $service_category): int
+    {
+        $this->validate($service_category);
+
+        if (empty($service_category['id']))
+        {
+            return $this->insert($service_category);
+        }
+        else
+        {
+            return $this->update($service_category);
+        }
+    }
+
+    /**
+     * Validate the service category data.
+     *
+     * @param array $service_category Associative array with the service category data.
+     *
+     * @throws InvalidArgumentException
+     */
+    public function validate(array $service_category): void
+    {
+        // If a service category ID is provided then check whether the record really exists in the database.
+        if ( ! empty($service_category['id']))
+        {
+            $count = $this->db->get_where('service_categories', ['id' => $service_category['id']])->num_rows();
+
+            if ( ! $count)
+            {
+                throw new InvalidArgumentException('The provided service category ID does not exist in the database: ' . $service_category['id']);
+            }
+        }
+
+        // Make sure all required fields are provided.
+        if (
+            empty($service_category['name'])
+        )
+        {
+            throw new InvalidArgumentException('Not all required fields are provided: ' . print_r($service_category, TRUE));
+        }
+    }
+
+    /**
+     * Insert a new service category into the database.
+     *
+     * @param array $service_category Associative array with the service category data.
+     *
+     * @return int Returns the service category ID.
+     *
+     * @throws RuntimeException
+     */
+    protected function insert(array $service_category): int
+    {
+        if ( ! $this->db->insert('service_categories', $service_category))
+        {
+            throw new RuntimeException('Could not insert service category.');
+        }
+
+        return $this->db->insert_id();
+    }
+
+    /**
+     * Update an existing service category.
+     *
+     * @param array $service_category Associative array with the service category data.
+     *
+     * @return int Returns the service category ID.
+     *
+     * @throws RuntimeException
+     */
+    protected function update(array $service_category): int
+    {
+        if ( ! $this->db->update('service_categories', $service_category, ['id' => $service_category['id']]))
+        {
+            throw new RuntimeException('Could not update service categories.');
+        }
+
+        return $service_category['id'];
+    }
+
+    /**
+     * Remove an existing service category from the database.
+     *
+     * @param int $service_category_id Service category ID.
+     *
+     * @throws RuntimeException
+     */
+    public function delete(int $service_category_id): void
+    {
+        if ( ! $this->db->delete('service_categories', ['id' => $service_category_id]))
+        {
+            throw new RuntimeException('Could not delete service categories.');
+        }
+    }
+
+    /**
+     * Get a specific service category from the database.
+     *
+     * @param int $service_category_id The ID of the record to be returned.
+     *
+     * @return array Returns an array with the service category data.
+     *
+     * @throws InvalidArgumentException
+     */
+    public function find(int $service_category_id): array
+    {
+        if ( ! $this->db->get_where('service_categories', ['id' => $service_category_id])->num_rows())
+        {
+            throw new InvalidArgumentException('The provided service category ID was not found in the database: ' . $service_category_id);
+        }
+
+        return $this->db->get_where('service_categories', ['id' => $service_category_id])->row_array();
+    }
+
+    /**
+     * Get a specific field value from the database.
+     *
+     * @param int $service_category_id Service category ID.
+     * @param string $field Name of the value to be returned.
+     *
+     * @return string Returns the selected service category value from the database.
+     *
+     * @throws InvalidArgumentException
+     */
+    public function value(int $service_category_id, string $field): string
+    {
+        if (empty($field))
+        {
+            throw new InvalidArgumentException('The field argument is cannot be empty.');
+        }
+
+        if (empty($service_category_id))
+        {
+            throw new InvalidArgumentException('The service category ID argument cannot be empty.');
+        }
+
+        // Check whether the service exists.
+        $query = $this->db->get_where('service_categories', ['id' => $service_category_id]);
+
+        if ( ! $query->num_rows())
+        {
+            throw new InvalidArgumentException('The provided service category ID was not found in the database: ' . $service_category_id);
+        }
+
+        // Check if the required field is part of the service category data.
+        $service_category = $query->row_array();
+
+        if ( ! array_key_exists($field, $service_category))
+        {
+            throw new InvalidArgumentException('The requested field was not found in the service category data: ' . $field);
+        }
+
+        return $service_category[$field];
+    }
+
+    /**
+     * Get all services that match the provided criteria.
+     *
+     * @param array|string $where Where conditions
+     * @param int|null $limit Record limit.
+     * @param int|null $offset Record offset.
+     * @param string|null $order_by Order by.
+     *
+     * @return array Returns an array of service categories.
+     */
+    public function get($where = NULL, int $limit = NULL, int $offset = NULL, string $order_by = NULL): array
+    {
+        if ($where !== NULL)
+        {
+            $this->db->where($where);
+        }
+
+        if ($order_by !== NULL)
+        {
+            $this->db->order_by($order_by);
+        }
+
+        return $this->db->get('service_categories', $limit, $offset)->result_array();
+    }
+
+    /**
+     * Get the query builder interface, configured for use with the service categories table.
+     *
+     * @return CI_DB_query_builder
+     */
+    public function query(): CI_DB_query_builder
+    {
+        return $this->db->from('service_categories');
+    }
+
+    /**
+     * Search service categories by the provided keyword.
+     *
+     * @param string $keyword Search keyword.
+     * @param int|null $limit Record limit.
+     * @param int|null $offset Record offset.
+     * @param string|null $order_by Order by.
+     *
+     * @return array Returns an array of service categories.
+     */
+    public function search(string $keyword, int $limit = NULL, int $offset = NULL, string $order_by = NULL): array
+    {
+        return $this
+            ->db
+            ->select()
+            ->from('service_categories')
+            ->like('name', $keyword)
+            ->or_like('description', $keyword)
+            ->limit($limit)
+            ->offset($offset)
+            ->order_by($order_by)
+            ->get()
+            ->result_array();
+    }
+
+    /**
+     * Attach related resources to a service category.
+     *
+     * @param array $service_category Associative array with the service category data.
+     * @param array $resources Resource names to be attached.
+     *
+     * @throws InvalidArgumentException
+     */
+    public function attach(array &$service_category, array $resources): void
+    {
+        // Service categories do not currently have any related resources. 
+    }
+}