diff --git a/CRM/Core/SelectValues.php b/CRM/Core/SelectValues.php
index de5668a6e779..9ebe8db0ce6f 100644
--- a/CRM/Core/SelectValues.php
+++ b/CRM/Core/SelectValues.php
@@ -443,6 +443,27 @@ public static function geoProvider() {
     return $geo;
   }
 
+  /**
+   * Get options for displaying tax.
+   *
+   * @return array
+   *
+   * @throws \CRM_Core_Exception
+   */
+  public function taxDisplayOptions() {
+    return [
+      'Do_not_show' => ts('Do not show breakdown, only show total - i.e %1', [
+        1 => CRM_Utils_Money::format(120),
+      ]),
+      'Inclusive' => ts('Show [tax term] inclusive price - i.e. %1', [
+        1 => ts('%1 (includes [tax term] of %2)', [1 => CRM_Utils_Money::format(120), 2 => CRM_Utils_Money::format(20)]),
+      ]),
+      'Exclusive' => ts('Show [tax term] exclusive price - i.e. %1', [
+        1 => ts('%1 + %2 [tax term]', [1 => CRM_Utils_Money::format(120), 2 => CRM_Utils_Money::format(20)]),
+      ]),
+    ];
+  }
+
   /**
    * Get the Address Standardization Providers from available plugins.
    *
diff --git a/CRM/Invoicing/Utils.php b/CRM/Invoicing/Utils.php
index 06b56fbab096..6f0bc50cf263 100644
--- a/CRM/Invoicing/Utils.php
+++ b/CRM/Invoicing/Utils.php
@@ -24,6 +24,8 @@ class CRM_Invoicing_Utils {
    * @param bool $oldValue
    * @param bool $newValue
    * @param array $metadata
+   *
+   * @throws \CiviCRM_API3_Exception
    */
   public static function onToggle($oldValue, $newValue, $metadata) {
     if ($oldValue == $newValue) {
@@ -32,7 +34,7 @@ public static function onToggle($oldValue, $newValue, $metadata) {
     $existingUserViewOptions = civicrm_api3('Setting', 'get', ['return' => 'user_dashboard_options'])['values'][CRM_Core_Config::domainID()]['user_dashboard_options'];
     $optionValues = civicrm_api3('Setting', 'getoptions', ['field' => 'user_dashboard_options'])['values'];
     $invoiceKey = array_search('Invoices / Credit Notes', $optionValues);
-    $existingIndex = in_array($invoiceKey, $existingUserViewOptions);
+    $existingIndex = array_search($invoiceKey, $existingUserViewOptions);
 
     if ($newValue && $existingIndex === FALSE) {
       $existingUserViewOptions[] = $invoiceKey;
diff --git a/CRM/Upgrade/Incremental/Base.php b/CRM/Upgrade/Incremental/Base.php
index bde6bb675bd4..0faa6012e410 100644
--- a/CRM/Upgrade/Incremental/Base.php
+++ b/CRM/Upgrade/Incremental/Base.php
@@ -9,6 +9,8 @@
  +--------------------------------------------------------------------+
  */
 
+use Civi\Core\SettingsBag;
+
 /**
  * Base class for incremental upgrades
  */
@@ -195,11 +197,16 @@ public static function updateMessageTemplates($ctx, $version) {
    * @return bool
    */
   public static function updateContributeSettings($ctx) {
-    $settings = Civi::settings()->get('contribution_invoice_settings');
-    $metadata = \Civi\Core\SettingsMetadata::getMetadata();
-    $conversions = array_intersect_key((array) $settings, $metadata);
-    foreach ($conversions as $key => $conversion) {
-      Civi::settings()->set($key, $conversion);
+    // Use a direct query as api now does some handling on this.
+    $settings = CRM_Core_DAO::executeQuery("SELECT value, domain_id FROM civicrm_setting WHERE name = 'contribution_invoice_settings'");
+
+    while ($settings->fetch()) {
+      $contributionSettings = (array) CRM_Utils_String::unserialize($settings->value);
+      foreach (array_merge(SettingsBag::getContributionInvoiceSettingKeys(), ['deferred_revenue_enabled' => 'deferred_revenue_enabled']) as $possibleKeyName => $settingName) {
+        if (!empty($contributionSettings[$possibleKeyName]) && empty(Civi::settings($settings->domain_id)->getExplicit($settingName))) {
+          Civi::settings($settings->domain_id)->set($settingName, $contributionSettings[$possibleKeyName]);
+        }
+      }
     }
     return TRUE;
   }
diff --git a/Civi/Core/SettingsBag.php b/Civi/Core/SettingsBag.php
index c94f3e7a89f6..779bc3a2302f 100644
--- a/Civi/Core/SettingsBag.php
+++ b/Civi/Core/SettingsBag.php
@@ -136,6 +136,7 @@ public function loadValues() {
       while ($dao->fetch()) {
         $this->values[$dao->name] = ($dao->value !== NULL) ? \CRM_Utils_String::unserialize($dao->value) : NULL;
       }
+      $dao->values['contribution_invoice_settings'] = $this->getContributionSettings();
     }
 
     return $this;
@@ -253,12 +254,51 @@ public function revert($key) {
    * @return SettingsBag
    */
   public function set($key, $value) {
+    if ($key === 'contribution_invoice_settings') {
+      $this->setContributionSettings($value);
+      return $this;
+    }
     $this->setDb($key, $value);
     $this->values[$key] = $value;
     $this->combined = NULL;
     return $this;
   }
 
+  /**
+   * Temporary handling for phasing out contribution_invoice_settings.
+   *
+   * Until we have transitioned we need to handle setting & retrieving
+   * contribution_invoice_settings.
+   *
+   * Once removed from core we will add deprecation notices & then remove this.
+   *
+   * https://lab.civicrm.org/dev/core/issues/1558
+   *
+   * @param array $value
+   */
+  public function setContributionSettings($value) {
+    foreach (SettingsBag::getContributionInvoiceSettingKeys() as $possibleKeyName => $settingName) {
+      $keyValue = $value[$possibleKeyName] ?? '';
+      $this->set($settingName, $keyValue);
+    }
+    $this->values['contribution_invoice_settings'] = $this->getContributionSettings();
+  }
+
+  /**
+   * Temporary function to handle returning the contribution_settings key despite it being deprecated.
+   *
+   * See more in comment block on previous function.
+   *
+   * @return array
+   */
+  public function getContributionSettings() {
+    $contributionSettings = [];
+    foreach (SettingsBag::getContributionInvoiceSettingKeys() as $keyName => $settingName) {
+      $contributionSettings[$keyName] = $this->values[$settingName] ?? '';
+    }
+    return $contributionSettings;
+  }
+
   /**
    * @return \CRM_Utils_SQL_Select
    */
@@ -378,4 +418,22 @@ protected function setDb($name, $value) {
     }
   }
 
+  /**
+   * @return array
+   */
+  public static function getContributionInvoiceSettingKeys(): array {
+    $convertedKeys = [
+      'credit_notes_prefix' => 'credit_notes_prefix',
+      'invoice_prefix' => 'invoice_prefix',
+      'due_date' => 'invoice_due_date',
+      'due_date_period' => 'invoice_due_date_period',
+      'notes' => 'invoice_notes',
+      'is_email_pdf'  => 'invoice_is_email_pdf',
+      'tax_term' => 'tax_term',
+      'tax_display_settings' => 'tax_display_settings',
+      'invoicing' => 'invoicing',
+    ];
+    return $convertedKeys;
+  }
+
 }
diff --git a/settings/Contribute.setting.php b/settings/Contribute.setting.php
index c48a906a3556..fb2170cc6ff4 100644
--- a/settings/Contribute.setting.php
+++ b/settings/Contribute.setting.php
@@ -50,7 +50,7 @@
       'tax_display_settings' => 'Inclusive',
     ],
     'add' => '4.7',
-    'title' => ts('Contribution Invoice Settings'),
+    'title' => ts('Deprecated setting'),
     'is_domain' => 1,
     'is_contact' => 0,
     'help_text' => NULL,
@@ -71,6 +71,97 @@
       'CRM_Invoicing_Utils::onToggle',
     ],
   ],
+  'credit_notes_prefix' => [
+    'group_name' => 'Contribute Preferences',
+    'group' => 'contribute',
+    'name' => 'credit_notes_prefix',
+    'html_type' => 'text',
+    'quick_form_type' => 'Element',
+    'add' => '5.23',
+    'type' => CRM_Utils_Type::T_STRING,
+    'title' => ts('Credit Notes Prefix'),
+    'is_domain' => 1,
+    'is_contact' => 0,
+    'description' => ts('Prefix to be prepended to credit note ids'),
+    'default' => 'CN_',
+    'help_text' => ts('The credit note ID is generated when a contribution is set to Refunded, Cancelled or Chargeback. It is visible on invoices, if invoices are enabled'),
+  ],
+  'invoice_prefix' => [
+    'html_type' => 'text',
+    'name' => 'invoice_prefix',
+    'add' => '5.23',
+    'type' => CRM_Utils_Type::T_STRING,
+    'title' => ts('Invoice Prefix'),
+    'description' => ts('Enter prefix to be be preprended when creating an invoice number'),
+    'is_domain' => 1,
+    'is_contact' => 0,
+  ],
+  'invoice_due_date' => [
+    'name' => 'invoice_due_date',
+    'html_type' => 'text',
+    'title' => ts('Due Date'),
+    'add' => '5.23',
+    'type' => CRM_Utils_Type::T_INT,
+    'is_domain' => 1,
+    'is_contact' => 0,
+  ],
+  'invoice_due_date_period' => [
+    'html_type' => 'select',
+    'name' => 'invoice_due_date_period',
+    'title' => ts('For transmission'),
+    'weight' => 4,
+    'add' => '5.23',
+    'type' => CRM_Utils_Type::T_STRING,
+    'is_domain' => 1,
+    'is_contact' => 0,
+    'description' => ts('Select the interval for due date.'),
+    'options' => [
+      'select' => ts('- select -'),
+      'days' => ts('Days'),
+      'months' => ts('Months'),
+      'years' => ts('Years'),
+    ],
+  ],
+  'invoice_notes' => [
+    'name' => 'invoice_notes',
+    'html_type' => 'wysiwyg',
+    'title' => ts('Notes or Standard Terms'),
+    'type' => CRM_Utils_Type::T_STRING,
+    'add' => '5.23',
+    'is_domain' => 1,
+    'is_contact' => 0,
+    'description' => ts('Enter note or message to be displayed on PDF invoice or credit notes '),
+    'attributes' => ['rows' => 2, 'cols' => 40],
+  ],
+  'invoice_is_email_pdf' => [
+    'name' => 'invoice_is_email_pdf',
+    'html_type' => 'checkbox',
+    'add' => '5.23',
+    'type' => CRM_Utils_Type::T_BOOLEAN,
+    'is_domain' => 1,
+    'is_contact' => 0,
+    'title' => ts('Automatically email invoice when user purchases online'),
+    'description' => ts('Should a pdf invoice be emailed automatically?'),
+  ],
+  'tax_term' => [
+    'name' => 'tax_term',
+    'html_type' => 'text',
+    'add' => '5.23',
+    'title' => ts('Tax Term'),
+    'type' => CRM_Utils_Type::T_STRING,
+    'is_domain' => 1,
+    'is_contact' => 0,
+  ],
+  'tax_display_settings' => [
+    'html_type' => 'select',
+    'name' => 'tax_display_settings',
+    'type' => CRM_Utils_Type::T_STRING,
+    'add' => '5.23',
+    'title' => ts('Tax Display Settings'),
+    'is_domain' => 1,
+    'is_contact' => 0,
+    'pseudoconstant' => ['callback' => 'CRM_Core_SelectValues::taxDisplayOptions'],
+  ],
   'acl_financial_type' => [
     'group_name' => 'Contribute Preferences',
     'group' => 'contribute',
diff --git a/tests/phpunit/CRM/Contact/Page/View/UserDashBoardTest.php b/tests/phpunit/CRM/Contact/Page/View/UserDashBoardTest.php
index e7f1538df89d..9bf3c6f6a764 100644
--- a/tests/phpunit/CRM/Contact/Page/View/UserDashBoardTest.php
+++ b/tests/phpunit/CRM/Contact/Page/View/UserDashBoardTest.php
@@ -135,6 +135,9 @@ public function testDashboardContentContributionsWithInvoicingEnabled() {
 
   /**
    * Test the content of the dashboard.
+   *
+   * @throws \CRM_Core_Exception
+   * @throws \CiviCRM_API3_Exception
    */
   public function testDashboardContentContributions() {
     $this->contributionCreate(['contact_id' => $this->contactID]);
diff --git a/tests/phpunit/CRM/Core/BAO/SettingTest.php b/tests/phpunit/CRM/Core/BAO/SettingTest.php
index c477fd041158..2901412599e2 100644
--- a/tests/phpunit/CRM/Core/BAO/SettingTest.php
+++ b/tests/phpunit/CRM/Core/BAO/SettingTest.php
@@ -29,31 +29,77 @@ public function tearDown() {
     parent::tearDown();
   }
 
+  /**
+   * Test that enabling a valid component works.
+   */
   public function testEnableComponentValid() {
-    $config = CRM_Core_Config::singleton(TRUE, TRUE);
-
+    CRM_Core_Config::singleton(TRUE, TRUE);
     $result = CRM_Core_BAO_ConfigSetting::enableComponent('CiviCampaign');
-
     $this->assertTrue($result);
   }
 
+  /**
+   * Test that we get a success result if we try to enable an enabled component.
+   */
   public function testEnableComponentAlreadyPresent() {
-    $config = CRM_Core_Config::singleton(TRUE, TRUE);
-
-    $result = CRM_Core_BAO_ConfigSetting::enableComponent('CiviCampaign');
+    CRM_Core_Config::singleton(TRUE, TRUE);
+    CRM_Core_BAO_ConfigSetting::enableComponent('CiviCampaign');
     $result = CRM_Core_BAO_ConfigSetting::enableComponent('CiviCampaign');
-
     $this->assertTrue($result);
   }
 
+  /**
+   * Test that we get a false result if we try to enable an invalid component.
+   */
   public function testEnableComponentInvalid() {
-    $config = CRM_Core_Config::singleton(TRUE, TRUE);
-
+    CRM_Core_Config::singleton(TRUE, TRUE);
     $result = CRM_Core_BAO_ConfigSetting::enableComponent('CiviFake');
-
     $this->assertFalse($result);
   }
 
+  /**
+   * Test temporary retrieval & setting of converted settings.
+   *
+   * As a transitional measure we allow the settings that were munged into
+   * contribution_invoice_setting. This tests that the current method of getting via the 'old' key
+   * works. This will be deprecated & removed over the next few versions but
+   * 1) some extensions use these settings &
+   * 2) there is a lot of work to fix this mess in core so a transitional method makes sense.
+   *
+   * https://lab.civicrm.org/dev/core/issues/1558
+   *
+   * @throws \CRM_Core_Exception
+   */
+  public function testHandlingOfContributionInvoiceSetting() {
+    $contributionSettings = [
+      'invoice_prefix' => 'G_',
+      'credit_notes_prefix' => 'XX_',
+      'due_date' => '20',
+      'due_date_period' => 'weeks',
+      'notes' => '<p>Give me money</p>',
+      'tax_term' => 'Extortion',
+      'tax_display_settings' => 'Exclusive',
+      'invoicing' => 1,
+      'is_email_pdf' => '1',
+    ];
+    Civi::settings()->set('contribution_invoice_settings', $contributionSettings);
+    $settingsFromGet = Civi::settings()->get('contribution_invoice_settings');
+    $settingsFromAPI = $this->callAPISuccess('Setting', 'get', ['return' => 'contribution_invoice_settings'])['values'][CRM_Core_Config::domainID()]['contribution_invoice_settings'];
+    $getVersion = $this->callAPISuccessGetValue('Setting', ['name' => 'contribution_invoice_settings']);
+    $this->assertEquals($settingsFromAPI, $settingsFromGet);
+    $this->assertAPIArrayComparison($getVersion, $settingsFromGet);
+    $this->assertEquals($contributionSettings, $settingsFromGet);
+
+    // These are the preferred retrieval methods.
+    $this->assertEquals('G_', Civi::settings()->get('invoice_prefix'));
+    $this->assertEquals('XX_', Civi::settings()->get('credit_notes_prefix'));
+    $this->assertEquals('20', Civi::settings()->get('invoice_due_date'));
+    $this->assertEquals('weeks', Civi::settings()->get('invoice_due_date_period'));
+    $this->assertEquals('<p>Give me money</p>', Civi::settings()->get('invoice_notes'));
+    $this->assertEquals('Extortion', Civi::settings()->get('tax_term'));
+    $this->assertEquals('Exclusive', Civi::settings()->get('tax_display_settings'));
+  }
+
   /**
    * Ensure that overrides in $civicrm_setting apply when
    * using getItem($group,$name).
diff --git a/tests/phpunit/CRM/Core/Payment/PayPalIPNTest.php b/tests/phpunit/CRM/Core/Payment/PayPalIPNTest.php
index 6af63c183807..d51650131795 100644
--- a/tests/phpunit/CRM/Core/Payment/PayPalIPNTest.php
+++ b/tests/phpunit/CRM/Core/Payment/PayPalIPNTest.php
@@ -57,6 +57,8 @@ public function tearDown() {
    *
    * The scenario is that a pending contribution exists and the IPN call will update it to completed.
    * And also if Tax and Invoicing is enabled, this unit test ensure that invoice pdf is attached with email recipet
+   *
+   * @throws \CRM_Core_Exception
    */
   public function testInvoiceSentOnIPNPaymentSuccess() {
     $this->enableTaxAndInvoicing();
@@ -81,7 +83,7 @@ public function testInvoiceSentOnIPNPaymentSuccess() {
     $_REQUEST = ['q' => CRM_Utils_System::url('civicrm/payment/ipn/' . $this->_paymentProcessorID)] + $this->getPaypalTransaction();
 
     $mut = new CiviMailUtils($this, TRUE);
-    $paymentProcesors = civicrm_api3('PaymentProcessor', 'getsingle', ['id' => $this->_paymentProcessorID]);
+    $paymentProcesors = $this->callAPISuccessGetSingle('PaymentProcessor', ['id' => $this->_paymentProcessorID]);
     $payment = Civi\Payment\System::singleton()->getByProcessor($paymentProcesors);
     $payment->handlePaymentNotification();
 
diff --git a/tests/phpunit/CRM/Financial/BAO/FinancialAccountTest.php b/tests/phpunit/CRM/Financial/BAO/FinancialAccountTest.php
index 773188695cec..699815bf2ac0 100644
--- a/tests/phpunit/CRM/Financial/BAO/FinancialAccountTest.php
+++ b/tests/phpunit/CRM/Financial/BAO/FinancialAccountTest.php
@@ -360,7 +360,7 @@ public function testBalanceDueIfDeferredRevenueEnabled() {
     ]);
     $balance = CRM_Contribute_BAO_Contribution::getContributionBalance($contribution['id'], $totalAmount);
     $this->assertEquals(0.0, $balance);
-    Civi::settings()->revert('contribution_invoice_settings');
+    Civi::settings()->set('deferred_revenue_enabled', FALSE);
   }
 
   /**
diff --git a/tests/phpunit/CRM/Upgrade/Incremental/BaseTest.php b/tests/phpunit/CRM/Upgrade/Incremental/BaseTest.php
index 238816045d21..a08f02950f55 100644
--- a/tests/phpunit/CRM/Upgrade/Incremental/BaseTest.php
+++ b/tests/phpunit/CRM/Upgrade/Incremental/BaseTest.php
@@ -461,10 +461,27 @@ public function testRenameFields() {
    * 'proper' setting.
    */
   public function testConvertUpgradeContributeSettings() {
-    Civi::settings()->set('contribution_invoice_settings', ['foo' => 'bar', 'deferred_revenue_enabled' => 1]);
-    $this->assertEquals(0, Civi::settings()->get('deferred_revenue_enabled'));
+    $setting = [
+      'deferred_revenue_enabled' => 1,
+      'invoice_prefix' => 'G_',
+      'credit_notes_prefix' => 'XX_',
+      'due_date' => '20',
+      'due_date_period' => 'weeks',
+      'notes' => '<p>Give me money</p>',
+      'tax_term' => 'Extortion',
+      'tax_display_settings' => 'Exclusive',
+    ];
+    CRM_Core_DAO::executeQuery("INSERT INTO civicrm_setting (name, domain_id, value)
+    VALUES ('contribution_invoice_settings', 1, '" . serialize($setting) . "')");
     CRM_Upgrade_Incremental_Base::updateContributeSettings(NULL, 5.1);
     $this->assertEquals(1, Civi::settings()->get('deferred_revenue_enabled'));
+    $this->assertEquals('G_', Civi::settings()->get('invoice_prefix'));
+    $this->assertEquals('XX_', Civi::settings()->get('credit_notes_prefix'));
+    $this->assertEquals('20', Civi::settings()->get('invoice_due_date'));
+    $this->assertEquals('weeks', Civi::settings()->get('invoice_due_date_period'));
+    $this->assertEquals('<p>Give me money</p>', Civi::settings()->get('invoice_notes'));
+    $this->assertEquals('Extortion', Civi::settings()->get('tax_term'));
+    $this->assertEquals('Exclusive', Civi::settings()->get('tax_display_settings'));
   }
 
   /**