diff --git a/spec/Entity/CreditMemoSequenceSpec.php b/spec/Entity/CreditMemoSequenceSpec.php
index 39493b43..ee5895a1 100644
--- a/spec/Entity/CreditMemoSequenceSpec.php
+++ b/spec/Entity/CreditMemoSequenceSpec.php
@@ -14,6 +14,11 @@ function it_implements_sequence_interface(): void
         $this->shouldImplement(SequenceInterface::class);
     }
 
+    function it_has_no_id_by_default(): void
+    {
+        $this->getId()->shouldReturn(null);
+    }
+
     function it_has_incrementable_index(): void
     {
         $this->getIndex()->shouldReturn(0);
diff --git a/spec/Entity/CustomerBillingDataSpec.php b/spec/Entity/CustomerBillingDataSpec.php
index 9221f1e8..12e15e89 100644
--- a/spec/Entity/CustomerBillingDataSpec.php
+++ b/spec/Entity/CustomerBillingDataSpec.php
@@ -28,6 +28,11 @@ function it_implements_customer_billing_data_interface(): void
         $this->shouldImplement(CustomerBillingDataInterface::class);
     }
 
+    function it_has_no_id_by_default(): void
+    {
+        $this->id()->shouldReturn(null);
+    }
+
     function it_has_customer_name(): void
     {
         $this->customerName()->shouldReturn('Rick Sanchez');
diff --git a/spec/Entity/LineItemSpec.php b/spec/Entity/LineItemSpec.php
index ea80c17e..3a447fbd 100644
--- a/spec/Entity/LineItemSpec.php
+++ b/spec/Entity/LineItemSpec.php
@@ -26,6 +26,12 @@ function it_implements_resource_interface(): void
         $this->shouldImplement(ResourceInterface::class);
     }
 
+    function it_has_no_id_by_default(): void
+    {
+        $this->getId()->shouldReturn(null);
+        $this->id()->shouldReturn(null);
+    }
+
     function it_has_proper_line_item_data(): void
     {
         $this->name()->shouldReturn('Mjolnir');
diff --git a/spec/Entity/RefundPaymentSpec.php b/spec/Entity/RefundPaymentSpec.php
index 42bd8dd3..43adf835 100644
--- a/spec/Entity/RefundPaymentSpec.php
+++ b/spec/Entity/RefundPaymentSpec.php
@@ -26,6 +26,11 @@ function it_implements_refund_payment_interface(): void
         $this->shouldImplement(RefundPaymentInterface::class);
     }
 
+    function it_has_no_id_by_default(): void
+    {
+        $this->getId()->shouldReturn(null);
+    }
+
     function it_has_order_number(): void
     {
         $this->getOrderNumber()->shouldReturn('000002');
diff --git a/spec/Entity/RefundSpec.php b/spec/Entity/RefundSpec.php
index cbc3b088..8d7f1230 100644
--- a/spec/Entity/RefundSpec.php
+++ b/spec/Entity/RefundSpec.php
@@ -20,6 +20,11 @@ function it_implements_refund_interface(): void
         $this->shouldImplement(RefundInterface::class);
     }
 
+    function it_has_no_id_by_default(): void
+    {
+        $this->getId()->shouldReturn(null);
+    }
+
     function it_has_order_number(): void
     {
         $this->getOrderNumber()->shouldReturn('000666');
diff --git a/spec/Entity/ShopBillingDataSpec.php b/spec/Entity/ShopBillingDataSpec.php
index ed251d4c..d264b6db 100644
--- a/spec/Entity/ShopBillingDataSpec.php
+++ b/spec/Entity/ShopBillingDataSpec.php
@@ -19,6 +19,11 @@ function it_implements_shop_billing_data_interface(): void
         $this->shouldImplement(ShopBillingDataInterface::class);
     }
 
+    function it_has_no_id_by_default(): void
+    {
+        $this->id()->shouldReturn(null);
+    }
+
     function it_has_company(): void
     {
         $this->company()->shouldReturn('Needful Things');
diff --git a/spec/Entity/TaxItemSpec.php b/spec/Entity/TaxItemSpec.php
index a4729369..c434f4c8 100644
--- a/spec/Entity/TaxItemSpec.php
+++ b/spec/Entity/TaxItemSpec.php
@@ -19,6 +19,12 @@ function it_implements_tax_item_interface(): void
         $this->shouldImplement(TaxItemInterface::class);
     }
 
+    function it_has_no_id_by_default(): void
+    {
+        $this->getId()->shouldReturn(null);
+        $this->id()->shouldReturn(null);
+    }
+
     function it_has_a_label(): void
     {
         $this->label()->shouldReturn('VAT');
diff --git a/src/Entity/CreditMemoSequence.php b/src/Entity/CreditMemoSequence.php
index 2998b6f3..a8d32806 100644
--- a/src/Entity/CreditMemoSequence.php
+++ b/src/Entity/CreditMemoSequence.php
@@ -7,7 +7,7 @@
 /** @final */
 class CreditMemoSequence implements SequenceInterface
 {
-    /** @var int */
+    /** @var int|null */
     protected $id;
 
     /** @var int */
@@ -16,7 +16,7 @@ class CreditMemoSequence implements SequenceInterface
     /** @var int */
     protected $version = 1;
 
-    public function getId(): int
+    public function getId(): ?int
     {
         return $this->id;
     }
diff --git a/src/Entity/CustomerBillingData.php b/src/Entity/CustomerBillingData.php
index 0d847859..141387f5 100644
--- a/src/Entity/CustomerBillingData.php
+++ b/src/Entity/CustomerBillingData.php
@@ -7,7 +7,7 @@
 /** @final */
 class CustomerBillingData implements CustomerBillingDataInterface
 {
-    /** @var int */
+    /** @var int|null */
     protected $id;
 
     /** @var string */
@@ -54,7 +54,7 @@ public function __construct(
         $this->provinceCode = $provinceCode;
     }
 
-    public function id(): int
+    public function id(): ?int
     {
         return $this->id;
     }
diff --git a/src/Entity/CustomerBillingDataInterface.php b/src/Entity/CustomerBillingDataInterface.php
index adcdab28..86e14d36 100644
--- a/src/Entity/CustomerBillingDataInterface.php
+++ b/src/Entity/CustomerBillingDataInterface.php
@@ -15,7 +15,7 @@
 
 interface CustomerBillingDataInterface
 {
-    public function id(): int;
+    public function id(): ?int;
 
     public function customerName(): string;
 
diff --git a/src/Entity/LineItem.php b/src/Entity/LineItem.php
index c082a414..18685bba 100644
--- a/src/Entity/LineItem.php
+++ b/src/Entity/LineItem.php
@@ -9,7 +9,7 @@
 /** @final */
 class LineItem implements LineItemInterface
 {
-    /** @var int */
+    /** @var int|null */
     protected $id;
 
     /** @var string */
@@ -56,12 +56,12 @@ public function __construct(
         $this->taxRate = $taxRate;
     }
 
-    public function getId(): int
+    public function getId(): ?int
     {
         return $this->id();
     }
 
-    public function id(): int
+    public function id(): ?int
     {
         return $this->id;
     }
diff --git a/src/Entity/LineItemInterface.php b/src/Entity/LineItemInterface.php
index 644ec1a9..92d49fd8 100644
--- a/src/Entity/LineItemInterface.php
+++ b/src/Entity/LineItemInterface.php
@@ -8,7 +8,7 @@
 
 interface LineItemInterface extends ResourceInterface
 {
-    public function id(): int;
+    public function id(): ?int;
 
     public function name(): string;
 
diff --git a/src/Entity/RefundPayment.php b/src/Entity/RefundPayment.php
index 66fdf7fa..6f21d409 100644
--- a/src/Entity/RefundPayment.php
+++ b/src/Entity/RefundPayment.php
@@ -9,7 +9,7 @@
 /** @final */
 class RefundPayment implements RefundPaymentInterface
 {
-    /** @var int */
+    /** @var int|null */
     protected $id;
 
     /** @var string */
@@ -41,6 +41,11 @@ public function __construct(
         $this->paymentMethod = $paymentMethod;
     }
 
+    public function getId(): ?int
+    {
+        return $this->id;
+    }
+
     public function getOrderNumber(): string
     {
         return $this->orderNumber;
@@ -66,11 +71,6 @@ public function setState(string $state): void
         $this->state = $state;
     }
 
-    public function getId(): int
-    {
-        return $this->id;
-    }
-
     public function getPaymentMethod(): PaymentMethodInterface
     {
         return $this->paymentMethod;
diff --git a/src/Entity/SequenceInterface.php b/src/Entity/SequenceInterface.php
index dda1daa8..e8135b39 100644
--- a/src/Entity/SequenceInterface.php
+++ b/src/Entity/SequenceInterface.php
@@ -6,7 +6,7 @@
 
 interface SequenceInterface
 {
-    public function getId(): int;
+    public function getId(): ?int;
 
     public function getIndex(): int;
 
diff --git a/src/Entity/ShopBillingData.php b/src/Entity/ShopBillingData.php
index 7ad98066..e0b3bbbc 100644
--- a/src/Entity/ShopBillingData.php
+++ b/src/Entity/ShopBillingData.php
@@ -7,7 +7,7 @@
 /** final */
 class ShopBillingData implements ShopBillingDataInterface
 {
-    /** @var int */
+    /** @var int|null */
     protected $id;
 
     /** @var string|null */
@@ -44,7 +44,7 @@ public function __construct(
         $this->postcode = $postcode;
     }
 
-    public function id(): int
+    public function id(): ?int
     {
         return $this->id;
     }
diff --git a/src/Entity/ShopBillingDataInterface.php b/src/Entity/ShopBillingDataInterface.php
index 152167ac..09686d5c 100644
--- a/src/Entity/ShopBillingDataInterface.php
+++ b/src/Entity/ShopBillingDataInterface.php
@@ -15,7 +15,7 @@
 
 interface ShopBillingDataInterface
 {
-    public function id(): int;
+    public function id(): ?int;
 
     public function company(): ?string;
 
diff --git a/src/Entity/TaxItem.php b/src/Entity/TaxItem.php
index 22493788..0aa5fe6f 100644
--- a/src/Entity/TaxItem.php
+++ b/src/Entity/TaxItem.php
@@ -7,7 +7,7 @@
 /** @final */
 class TaxItem implements TaxItemInterface
 {
-    /** @var int */
+    /** @var int|null */
     protected $id;
 
     /** @var string */
@@ -22,12 +22,12 @@ public function __construct(string $label, int $amount)
         $this->amount = $amount;
     }
 
-    public function getId(): int
+    public function getId(): ?int
     {
         return $this->id();
     }
 
-    public function id(): int
+    public function id(): ?int
     {
         return $this->id;
     }
diff --git a/src/Entity/TaxItemInterface.php b/src/Entity/TaxItemInterface.php
index f7ee4a2e..93dafdec 100644
--- a/src/Entity/TaxItemInterface.php
+++ b/src/Entity/TaxItemInterface.php
@@ -8,7 +8,7 @@
 
 interface TaxItemInterface extends ResourceInterface
 {
-    public function id(): int;
+    public function id(): ?int;
 
     public function label(): string;
 
diff --git a/src/Resources/config/doctrine/CreditMemo.orm.xml b/src/Resources/config/doctrine/CreditMemo.orm.xml
index 72923f68..724bb790 100644
--- a/src/Resources/config/doctrine/CreditMemo.orm.xml
+++ b/src/Resources/config/doctrine/CreditMemo.orm.xml
@@ -9,11 +9,11 @@
     <mapped-superclass name="Sylius\RefundPlugin\Entity\CreditMemo" table="sylius_refund_credit_memo">
         <id name="id" column="id" type="string" />
 
-        <field name="number" />
-        <field name="total" type="integer" />
-        <field name="currencyCode" column="currency_code" />
-        <field name="localeCode" column="locale_code" />
-        <field name="comment" type="text" />
+        <field name="number" column="number" type="string" />
+        <field name="total" column="total" type="integer" />
+        <field name="currencyCode" column="currency_code" type="string" />
+        <field name="localeCode" column="locale_code" type="string" />
+        <field name="comment" column="comment" type="text" />
         <field name="issuedAt" column="issued_at" type="datetime" nullable="true" />
 
         <many-to-one field="channel" target-entity="Sylius\Component\Core\Model\ChannelInterface">
diff --git a/src/Resources/config/doctrine/CreditMemoSequence.orm.xml b/src/Resources/config/doctrine/CreditMemoSequence.orm.xml
index d452ec3b..dee0a772 100644
--- a/src/Resources/config/doctrine/CreditMemoSequence.orm.xml
+++ b/src/Resources/config/doctrine/CreditMemoSequence.orm.xml
@@ -10,7 +10,8 @@
         <id name="id" column="id" type="integer">
             <generator strategy="AUTO" />
         </id>
+
         <field name="index" column="idx" type="integer" />
-        <field name="version" type="integer" version="true" />
+        <field name="version" column="version" type="integer" version="true" />
     </entity>
 </doctrine-mapping>
diff --git a/src/Resources/config/doctrine/CustomerBillingData.orm.xml b/src/Resources/config/doctrine/CustomerBillingData.orm.xml
index 189c6414..668d22d5 100644
--- a/src/Resources/config/doctrine/CustomerBillingData.orm.xml
+++ b/src/Resources/config/doctrine/CustomerBillingData.orm.xml
@@ -11,13 +11,13 @@
             <generator strategy="AUTO" />
         </id>
 
-        <field name="customerName" column="customer_name"/>
-        <field name="street" />
-        <field name="postcode" />
-        <field name="countryCode" column="country_code"/>
-        <field name="city" />
-        <field name="company" nullable="true" />
-        <field name="provinceName" column="province_name" nullable="true" />
-        <field name="provinceCode" column="province_code" nullable="true" />
+        <field name="customerName" column="customer_name" type="string" />
+        <field name="street" column="street" type="string" />
+        <field name="postcode" column="postcode" type="string" />
+        <field name="countryCode" column="country_code" type="string" />
+        <field name="city" column="city" type="string" />
+        <field name="company" column="company" type="string" nullable="true" />
+        <field name="provinceName" column="province_name" type="string" nullable="true" />
+        <field name="provinceCode" column="province_code" type="string" nullable="true" />
     </entity>
 </doctrine-mapping>
diff --git a/src/Resources/config/doctrine/LineItem.orm.xml b/src/Resources/config/doctrine/LineItem.orm.xml
index f078f1eb..3b072b5e 100644
--- a/src/Resources/config/doctrine/LineItem.orm.xml
+++ b/src/Resources/config/doctrine/LineItem.orm.xml
@@ -3,16 +3,16 @@
 <doctrine-mapping xmlns="http://doctrine-project.org/schemas/orm/doctrine-mapping" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://doctrine-project.org/schemas/orm/doctrine-mapping http://doctrine-project.org/schemas/orm/doctrine-mapping.xsd">
     <mapped-superclass name="Sylius\RefundPlugin\Entity\LineItem" table="sylius_refund_line_item">
         <id name="id" column="id" type="integer">
-            <generator />
+            <generator strategy="AUTO" />
         </id>
 
-        <field name="name" />
-        <field name="quantity" type="integer" />
+        <field name="name" column="name" type="string" />
+        <field name="quantity" column="quantity" type="integer" />
         <field name="unitNetPrice" column="unit_net_price" type="integer" />
         <field name="unitGrossPrice" column="unit_gross_price" type="integer" />
         <field name="netValue" column="net_value" type="integer" />
         <field name="grossValue" column="gross_value" type="integer" />
         <field name="taxAmount" column="tax_amount" type="integer" />
-        <field name="taxRate" column="tax_rate" nullable="true" />
+        <field name="taxRate" column="tax_rate" type="string" nullable="true" />
     </mapped-superclass>
 </doctrine-mapping>
diff --git a/src/Resources/config/doctrine/Refund.orm.xml b/src/Resources/config/doctrine/Refund.orm.xml
index 25da7280..75b22e3b 100644
--- a/src/Resources/config/doctrine/Refund.orm.xml
+++ b/src/Resources/config/doctrine/Refund.orm.xml
@@ -11,9 +11,9 @@
             <generator strategy="AUTO" />
         </id>
 
-        <field name="orderNumber" column="order_number" />
-        <field name="amount" type="integer" />
-        <field name="refundedUnitId" type="integer" nullable="true" column="refunded_unit_id"/>
-        <field name="type" type="sylius_refund_refund_type" />
+        <field name="orderNumber" column="order_number" type="string" />
+        <field name="amount" column="amount" type="integer" />
+        <field name="refundedUnitId" column="refunded_unit_id" type="integer" nullable="true" />
+        <field name="type" column="type" type="sylius_refund_refund_type" />
     </mapped-superclass>
 </doctrine-mapping>
diff --git a/src/Resources/config/doctrine/RefundPayment.orm.xml b/src/Resources/config/doctrine/RefundPayment.orm.xml
index 4bc732b8..38c829af 100644
--- a/src/Resources/config/doctrine/RefundPayment.orm.xml
+++ b/src/Resources/config/doctrine/RefundPayment.orm.xml
@@ -11,10 +11,10 @@
             <generator strategy="AUTO" />
         </id>
 
-        <field name="orderNumber" column="order_number"/>
-        <field name="amount" type="integer" />
-        <field name="currencyCode" column="currency_code"/>
-        <field name="state" />
+        <field name="orderNumber" column="order_number" type="string" />
+        <field name="amount" column="amount" type="integer" />
+        <field name="currencyCode" column="currency_code" type="string" />
+        <field name="state" column="state" type="string" />
 
         <many-to-one field="paymentMethod" target-entity="Sylius\Component\Payment\Model\PaymentMethodInterface">
             <join-column name="payment_method_id" referenced-column-name="id" nullable="true" />
diff --git a/src/Resources/config/doctrine/ShopBillingData.orm.xml b/src/Resources/config/doctrine/ShopBillingData.orm.xml
index f2efc3d2..87608f45 100644
--- a/src/Resources/config/doctrine/ShopBillingData.orm.xml
+++ b/src/Resources/config/doctrine/ShopBillingData.orm.xml
@@ -11,11 +11,11 @@
             <generator strategy="AUTO" />
         </id>
 
-        <field name="company" nullable="true" />
-        <field name="taxId" column="tax_id" nullable="true" />
-        <field name="countryCode" column="country_code" nullable="true" />
-        <field name="street" nullable="true" />
-        <field name="city" nullable="true" />
-        <field name="postcode" nullable="true" />
+        <field name="company" column="company" type="string" nullable="true" />
+        <field name="taxId" column="tax_id" type="string" nullable="true" />
+        <field name="countryCode" column="country_code" type="string" nullable="true" />
+        <field name="street" column="street" type="string" nullable="true" />
+        <field name="city" column="city" type="string" nullable="true" />
+        <field name="postcode" column="postcode" type="string" nullable="true" />
     </entity>
 </doctrine-mapping>
diff --git a/src/Resources/config/doctrine/TaxItem.orm.xml b/src/Resources/config/doctrine/TaxItem.orm.xml
index 6c06fa2e..1d27cab9 100644
--- a/src/Resources/config/doctrine/TaxItem.orm.xml
+++ b/src/Resources/config/doctrine/TaxItem.orm.xml
@@ -6,10 +6,10 @@
 >
     <mapped-superclass name="Sylius\RefundPlugin\Entity\TaxItem" table="sylius_refund_tax_item">
         <id name="id" column="id" type="integer">
-            <generator />
+            <generator strategy="AUTO" />
         </id>
 
-        <field name="label" />
-        <field name="amount" type="integer" />
+        <field name="label" column="label" type="string" />
+        <field name="amount" column="amount" type="integer" />
     </mapped-superclass>
 </doctrine-mapping>