diff --git a/src/core/providers/payment-flow/GCProvider.ts b/src/core/providers/payment-flow/GCProvider.ts
index 82786e183..87eb1caf5 100644
--- a/src/core/providers/payment-flow/GCProvider.ts
+++ b/src/core/providers/payment-flow/GCProvider.ts
@@ -31,9 +31,9 @@ class GCProvider implements PaymentFlowProvider {
     log.info("Created redirect flow " + redirectFlow.id);
 
     return {
-      id: redirectFlow.id,
+      id: redirectFlow.id!,
       params: {
-        redirectUrl: redirectFlow.redirect_url
+        redirectUrl: redirectFlow.redirect_url!
       }
     };
   }
@@ -49,8 +49,8 @@ class GCProvider implements PaymentFlowProvider {
 
     return {
       paymentMethod: joinFlow.joinForm.paymentMethod,
-      customerId: redirectFlow.links.customer,
-      mandateId: redirectFlow.links.mandate
+      customerId: redirectFlow.links!.customer!,
+      mandateId: redirectFlow.links!.mandate!
     };
   }
 
@@ -66,7 +66,7 @@ class GCProvider implements PaymentFlowProvider {
       ...(customer.family_name && { lastname: customer.family_name }),
       billingAddress: {
         line1: customer.address_line1 || "",
-        line2: customer.address_line2,
+        line2: customer.address_line2 || undefined,
         city: customer.city || "",
         postcode: customer.postal_code || ""
       }
diff --git a/src/core/providers/payment/GCProvider.ts b/src/core/providers/payment/GCProvider.ts
index 9a864050c..a81721383 100644
--- a/src/core/providers/payment/GCProvider.ts
+++ b/src/core/providers/payment/GCProvider.ts
@@ -39,14 +39,14 @@ export default class GCProvider extends PaymentProvider<GCPaymentData> {
       try {
         const mandate = await gocardless.mandates.get(this.data.mandateId);
         const bankAccount = await gocardless.customerBankAccounts.get(
-          mandate.links.customer_bank_account
+          mandate.links!.customer_bank_account!
         );
 
         paymentSource = {
           method: PaymentMethod.GoCardlessDirectDebit,
-          bankName: bankAccount.bank_name,
-          accountHolderName: bankAccount.account_holder_name,
-          accountNumberEnding: bankAccount.account_number_ending
+          bankName: bankAccount.bank_name || "",
+          accountHolderName: bankAccount.account_holder_name || "",
+          accountNumberEnding: bankAccount.account_number_ending || ""
         };
         pendingPayment = await hasPendingPayment(this.data.mandateId);
       } catch (err: any) {
@@ -148,7 +148,7 @@ export default class GCProvider extends PaymentProvider<GCPaymentData> {
     });
 
     this.data.cancelledAt = null;
-    this.data.subscriptionId = subscription.id;
+    this.data.subscriptionId = subscription.id!;
     this.data.payFee = paymentForm.payFee;
     this.data.nextMonthlyAmount = startNow ? null : paymentForm.monthlyAmount;
 
diff --git a/src/core/utils/payment/gocardless.ts b/src/core/utils/payment/gocardless.ts
index 6fafc7a82..a922df8ac 100644
--- a/src/core/utils/payment/gocardless.ts
+++ b/src/core/utils/payment/gocardless.ts
@@ -63,7 +63,7 @@ export async function getSubscriptionNextChargeDate(
   // include pending payments
   const date = pendingPayment
     ? pendingPayment.charge_date
-    : subscription.upcoming_payments[0].charge_date;
+    : subscription.upcoming_payments![0].charge_date;
   return moment.utc(date).add(config.gracePeriod).toDate();
 }
 
@@ -84,7 +84,7 @@ export async function createSubscription(
     const mandate = await gocardless.mandates.get(mandateId);
     // next_possible_charge_date will always have a value as this is an active mandate
     if (startDate < mandate.next_possible_charge_date!) {
-      startDate = mandate.next_possible_charge_date;
+      startDate = mandate.next_possible_charge_date!;
     }
   }
 
diff --git a/src/webhooks/handlers/gocardless.ts b/src/webhooks/handlers/gocardless.ts
index 9d054fe06..5c4a9b822 100644
--- a/src/webhooks/handlers/gocardless.ts
+++ b/src/webhooks/handlers/gocardless.ts
@@ -83,10 +83,10 @@ async function handlePaymentResourceEvent(event: Event) {
   // limited. It seems like we can pretty safely assume paid out payments
   // haven't changed though.
   if (event.action === PaymentStatus.PaidOut) {
-    await updatePaymentStatus(event.links.payment, PaymentStatus.PaidOut);
+    await updatePaymentStatus(event.links!.payment!, PaymentStatus.PaidOut);
   } else {
     await updatePayment(
-      event.links.payment,
+      event.links!.payment!,
       event.action === PaymentStatus.Confirmed
     );
   }
@@ -103,7 +103,7 @@ async function handleSubscriptionResourceEvent(event: Event) {
     case "customer_approval_denied":
     case "cancelled":
     case "finished":
-      await cancelSubscription(event.links.subscription);
+      await cancelSubscription(event.links!.subscription!);
       break;
   }
 }
@@ -128,14 +128,14 @@ async function handleMandateResourceEvent(event: Event) {
     case "failed":
     case "expired":
       // Remove the mandate from the database
-      await cancelMandate(event.links.mandate);
+      await cancelMandate(event.links!.mandate!);
       break;
   }
 }
 
 async function handleRefundResourceEvent(event: Event) {
-  const refund = await gocardless.refunds.get(event.links.refund);
-  await updatePayment(refund.links.payment);
+  const refund = await gocardless.refunds.get(event.links!.refund!);
+  await updatePayment(refund.links!.payment!);
 }
 
 export default app;
diff --git a/src/webhooks/utils/gocardless.ts b/src/webhooks/utils/gocardless.ts
index 6882f0229..39fb0a797 100644
--- a/src/webhooks/utils/gocardless.ts
+++ b/src/webhooks/utils/gocardless.ts
@@ -31,7 +31,7 @@ export async function updatePayment(
   const payment = await findOrCreatePayment(gcPayment);
 
   if (payment) {
-    payment.status = convertStatus(gcPayment.status);
+    payment.status = convertStatus(gcPayment.status!);
     payment.description = gcPayment.description || "Unknown";
     payment.amount = Number(gcPayment.amount) / 100;
     payment.amountRefunded = Number(gcPayment.amount_refunded) / 100;
@@ -68,7 +68,7 @@ async function confirmPayment(
   if (payment.subscriptionId !== gcData.subscriptionId) {
     log.error("Mismatched subscription IDs for payment " + payment.id, {
       ourSubscriptionId: payment.subscriptionId,
-      gcSubscriptionId: gcPayment.links.subscription
+      gcSubscriptionId: gcPayment.links!.subscription
     });
     return;
   }
@@ -101,7 +101,10 @@ async function getSubscriptionPeriodEnd(payment: Payment): Promise<Date> {
   );
 
   // If the subscription has been cancelled there won't be any upcoming payments
-  if (subscription.upcoming_payments.length > 0) {
+  if (
+    subscription.upcoming_payments &&
+    subscription.upcoming_payments.length > 0
+  ) {
     return moment
       .utc(subscription.upcoming_payments[0].charge_date)
       .add(config.gracePeriod)
@@ -179,7 +182,7 @@ async function findOrCreatePayment(
 
   const data = await PaymentService.getDataBy(
     "mandateId",
-    gcPayment.links.mandate
+    gcPayment.links!.mandate!
   );
 
   if (data) {
@@ -188,9 +191,9 @@ async function findOrCreatePayment(
       gcPaymentId: gcPayment.id
     });
     const newPayment = new Payment();
-    newPayment.id = gcPayment.id;
+    newPayment.id = gcPayment.id!;
     newPayment.contact = data.contact;
-    if (gcPayment.links.subscription) {
+    if (gcPayment.links?.subscription) {
       newPayment.subscriptionId = gcPayment.links.subscription;
     }
     return newPayment;