diff --git a/Civi/Payment/PropertyBag.php b/Civi/Payment/PropertyBag.php
index 25e4a1d3698..f3ce9304fb1 100644
--- a/Civi/Payment/PropertyBag.php
+++ b/Civi/Payment/PropertyBag.php
@@ -26,13 +26,23 @@ class PropertyBag implements \ArrayAccess {
 
   protected static $propMap = [
     'amount'                      => TRUE,
+    'total_amount'                => 'amount',
     'billingStreetAddress'        => TRUE,
+    'billing_street_address'      => 'billingStreetAddress',
+    'street_address'              => 'billingStreetAddress',
     'billingSupplementalAddress1' => TRUE,
     'billingSupplementalAddress2' => TRUE,
     'billingSupplementalAddress3' => TRUE,
     'billingCity'                 => TRUE,
+    'billing_city'                => 'billingCity',
+    'city'                        => 'billingCity',
     'billingPostalCode'           => TRUE,
+    'billing_postal_code'         => 'billingPostalCode',
+    'postal_code'                 => 'billingPostalCode',
     'billingCounty'               => TRUE,
+    'billingStateProvince'        => TRUE,
+    'billing_state_province'      => 'billingStateProvince',
+    'state_province'              => 'billingStateProvince',
     'billingCountry'              => TRUE,
     'contactID'                   => TRUE,
     'contact_id'                  => 'contactID',
@@ -174,13 +184,16 @@ public function offsetGet($offset) {
       }
     }
 
+    // These lines are here (and not in try block) because the catch must only
+    // catch the case when the prop is custom.
+    $getter = 'get' . ucfirst($prop);
     if (!$this->getSuppressLegacyWarnings()) {
       CRM_Core_Error::deprecatedFunctionWarning(
         "get" . ucfirst($offset) . "()",
         "PropertyBag array access for core property '$offset'"
       );
     }
-    return $this->get($prop, 'default');
+    return $this->$getter('default');
   }
 
   /**
@@ -258,13 +271,18 @@ protected function handleLegacyPropNames($prop, $silent = FALSE) {
     if ($newName === NULL && substr($prop, -2) === '-' . \CRM_Core_BAO_LocationType::getBilling()
       && isset(static::$propMap[substr($prop, 0, -2)])
     ) {
-      $newName = substr($prop, 0, -2);
+      $billingAddressProp = substr($prop, 0, -2);
+      $newName = static::$propMap[$billingAddressProp] ?? NULL;
+      if ($newName === TRUE) {
+        // Good, modern name.
+        return $billingAddressProp;
+      }
     }
 
     if ($newName === NULL) {
       if ($silent) {
         // Only for use by offsetExists
-        return;
+        return NULL;
       }
       throw new \InvalidArgumentException("Unknown property '$prop'.");
     }
@@ -591,6 +609,27 @@ public function setBillingCounty($input, $label = 'default') {
     return $this->set('billingCounty', $label, (string) $input);
   }
 
+  /**
+   * BillingStateProvince getter.
+   *
+   * @return string
+   */
+  public function getBillingStateProvince($label = 'default') {
+    return $this->get('billingStateProvince', $label);
+  }
+
+  /**
+   * BillingStateProvince setter.
+   *
+   * Nb. we can't validate this unless we have the country ID too, so we don't.
+   *
+   * @param string $input
+   * @param string $label e.g. 'default'
+   */
+  public function setBillingStateProvince($input, $label = 'default') {
+    return $this->set('billingStateProvince', $label, (string) $input);
+  }
+
   /**
    * BillingCountry getter.
    *
@@ -717,6 +756,9 @@ public function setCurrency($value, $label = 'default') {
    * @return string
    */
   public function getDescription($label = 'default') {
+    if (!$this->has('description')) {
+      return '';
+    }
     return $this->get('description', $label);
   }
 
@@ -804,6 +846,9 @@ public function setFirstName($firstName, $label = 'default') {
    * @return string|null
    */
   public function getInvoiceID($label = 'default') {
+    if (!$this->has('invoiceID')) {
+      $this->set('invoiceID', $label, md5(uniqid(mt_rand(), TRUE)));
+    }
     return $this->get('invoiceID', $label);
   }