diff --git a/src/Subscription.php b/src/Subscription.php
index 9b49078e..ae719977 100644
--- a/src/Subscription.php
+++ b/src/Subscription.php
@@ -1042,7 +1042,7 @@ public function syncTaxRates()
     {
         $stripeSubscription = $this->asStripeSubscription();
 
-        $stripeSubscription->default_tax_rates = $this->user->taxRates();
+        $stripeSubscription->default_tax_rates = $this->user->taxRates() ?: '';
 
         $stripeSubscription->proration_behavior = $this->prorateBehavior();
 
@@ -1051,7 +1051,7 @@ public function syncTaxRates()
         foreach ($this->items as $item) {
             $stripeSubscriptionItem = $item->asStripeSubscriptionItem();
 
-            $stripeSubscriptionItem->tax_rates = $this->getPlanTaxRatesForPayload($item->stripe_plan);
+            $stripeSubscriptionItem->tax_rates = $this->getPlanTaxRatesForPayload($item->stripe_plan) ?: '';
 
             $stripeSubscriptionItem->proration_behavior = $this->prorateBehavior();