diff --git a/apps/taxes/graphql/subscriptions/OrderCancelled.graphql b/apps/taxes/graphql/subscriptions/OrderCancelled.graphql
index 07b2bc8..09e4176 100644
--- a/apps/taxes/graphql/subscriptions/OrderCancelled.graphql
+++ b/apps/taxes/graphql/subscriptions/OrderCancelled.graphql
@@ -1,9 +1,6 @@
 fragment OrderCancelledSubscription on Order {
   id
-  privateMetadata {
-    key
-    value
-  }
+  externalId: metafield(key: "externalId")
   channel {
     id
     slug
diff --git a/apps/taxes/src/modules/avatax/avatax-client.ts b/apps/taxes/src/modules/avatax/avatax-client.ts
index 53631d1..f57b8b8 100644
--- a/apps/taxes/src/modules/avatax/avatax-client.ts
+++ b/apps/taxes/src/modules/avatax/avatax-client.ts
@@ -53,6 +53,11 @@ export type ValidateAddressArgs = {
   address: AvataxAddress;
 };
 
+export type VoidTransactionArgs = {
+  transactionCode: string;
+  companyCode: string;
+};
+
 export class AvataxClient {
   private client: Avatax;
   private logger: Logger;
@@ -73,6 +78,16 @@ export class AvataxClient {
     return this.client.commitTransaction(args);
   }
 
+  async voidTransaction({
+    transactionCode,
+    companyCode,
+  }: {
+    transactionCode: string;
+    companyCode: string;
+  }) {
+    return this.client.voidTransaction({ transactionCode, companyCode });
+  }
+
   async validateAddress({ address }: ValidateAddressArgs) {
     return this.client.resolveAddress(address);
   }
diff --git a/apps/taxes/src/modules/avatax/avatax-webhook.service.ts b/apps/taxes/src/modules/avatax/avatax-webhook.service.ts
index 68ae0fa..08e890b 100644
--- a/apps/taxes/src/modules/avatax/avatax-webhook.service.ts
+++ b/apps/taxes/src/modules/avatax/avatax-webhook.service.ts
@@ -12,6 +12,8 @@ import { AvataxConfig, defaultAvataxConfig } from "./avatax-connection-schema";
 import { AvataxCalculateTaxesAdapter } from "./calculate-taxes/avatax-calculate-taxes-adapter";
 import { AvataxOrderCreatedAdapter } from "./order-created/avatax-order-created-adapter";
 import { AvataxOrderFulfilledAdapter } from "./order-fulfilled/avatax-order-fulfilled-adapter";
+import { AvataxOrderCancelledAdapter } from "./order-cancelled/avatax-order-cancelled-adapter";
+import { OrderCancelledPayload } from "../../pages/api/webhooks/order-cancelled";
 
 export class AvataxWebhookService implements ProviderWebhookService {
   config = defaultAvataxConfig;
@@ -52,9 +54,10 @@ export class AvataxWebhookService implements ProviderWebhookService {
     return response;
   }
 
-  async cancelOrder(payload: OrderCancelledEventSubscriptionFragment) {
-    // todo: implement
+  async cancelOrder(payload: OrderCancelledPayload) {
     this.logger.debug("cancelOrder", payload);
-    return { ok: true };
+    const adapter = new AvataxOrderCancelledAdapter(this.config);
+
+    await adapter.send(payload);
   }
 }
diff --git a/apps/taxes/src/modules/avatax/order-cancelled/avatax-order-cancelled-adapter.ts b/apps/taxes/src/modules/avatax/order-cancelled/avatax-order-cancelled-adapter.ts
new file mode 100644
index 0000000..d34cb73
--- /dev/null
+++ b/apps/taxes/src/modules/avatax/order-cancelled/avatax-order-cancelled-adapter.ts
@@ -0,0 +1,31 @@
+import { Logger, createLogger } from "../../../lib/logger";
+import { OrderCancelledPayload } from "../../../pages/api/webhooks/order-cancelled";
+import { WebhookAdapter } from "../../taxes/tax-webhook-adapter";
+import { AvataxClient, VoidTransactionArgs } from "../avatax-client";
+import { AvataxConfig } from "../avatax-connection-schema";
+import { AvataxOrderCancelledPayloadTransformer } from "./avatax-order-cancelled-payload-transformer";
+
+export type AvataxOrderCancelledTarget = VoidTransactionArgs;
+
+export class AvataxOrderCancelledAdapter implements WebhookAdapter<OrderCancelledPayload, void> {
+  private logger: Logger;
+
+  constructor(private readonly config: AvataxConfig) {
+    this.logger = createLogger({ name: "AvataxOrderCancelledAdapter" });
+  }
+
+  async send(payload: OrderCancelledPayload) {
+    this.logger.debug("Transforming the Saleor payload for cancelling transaction with Avatax...");
+
+    const payloadTransformer = new AvataxOrderCancelledPayloadTransformer(this.config);
+    const target = payloadTransformer.transform({ ...payload });
+
+    this.logger.debug("Calling Avatax commitTransaction with transformed payload...");
+
+    const client = new AvataxClient(this.config);
+
+    await client.voidTransaction(target);
+
+    this.logger.debug("Avatax commitTransaction succesfully responded");
+  }
+}
diff --git a/apps/taxes/src/modules/avatax/order-cancelled/avatax-order-cancelled-payload-transformer.ts b/apps/taxes/src/modules/avatax/order-cancelled/avatax-order-cancelled-payload-transformer.ts
new file mode 100644
index 0000000..779c530
--- /dev/null
+++ b/apps/taxes/src/modules/avatax/order-cancelled/avatax-order-cancelled-payload-transformer.ts
@@ -0,0 +1,21 @@
+import { OrderCancelledPayload } from "../../../pages/api/webhooks/order-cancelled";
+import { taxProviderUtils } from "../../taxes/tax-provider-utils";
+import { AvataxConfig } from "../avatax-connection-schema";
+import { AvataxOrderCancelledTarget } from "./avatax-order-cancelled-adapter";
+
+export class AvataxOrderCancelledPayloadTransformer {
+  constructor(private readonly config: AvataxConfig) {}
+
+  transform({ order }: OrderCancelledPayload): AvataxOrderCancelledTarget {
+    if (!order) {
+      throw new Error("Order is required");
+    }
+
+    const transactionCode = taxProviderUtils.resolveOptionalOrThrow(order.externalId);
+
+    return {
+      transactionCode,
+      companyCode: this.config.companyCode ?? "",
+    };
+  }
+}
diff --git a/apps/taxes/src/modules/taxes/get-active-connection-service.ts b/apps/taxes/src/modules/taxes/get-active-connection-service.ts
index 0a8e6e8..a50458e 100644
--- a/apps/taxes/src/modules/taxes/get-active-connection-service.ts
+++ b/apps/taxes/src/modules/taxes/get-active-connection-service.ts
@@ -13,6 +13,7 @@ import { AvataxWebhookService } from "../avatax/avatax-webhook.service";
 import { ProviderConnection } from "../provider-connections/provider-connections";
 import { TaxJarWebhookService } from "../taxjar/taxjar-webhook.service";
 import { ProviderWebhookService } from "./tax-provider-webhook";
+import { OrderCancelledPayload } from "../../pages/api/webhooks/order-cancelled";
 
 // todo: refactor to a factory
 class ActiveTaxProviderService implements ProviderWebhookService {
@@ -57,8 +58,8 @@ class ActiveTaxProviderService implements ProviderWebhookService {
     return this.client.fulfillOrder(payload);
   }
 
-  async cancelOrder(payload: OrderCancelledEventSubscriptionFragment) {
-    return this.client.cancelOrder(payload);
+  async cancelOrder(payload: OrderCancelledPayload) {
+    this.client.cancelOrder(payload);
   }
 }
 
diff --git a/apps/taxes/src/modules/taxes/tax-provider-utils.ts b/apps/taxes/src/modules/taxes/tax-provider-utils.ts
index 568ee54..8b11080 100644
--- a/apps/taxes/src/modules/taxes/tax-provider-utils.ts
+++ b/apps/taxes/src/modules/taxes/tax-provider-utils.ts
@@ -3,8 +3,8 @@
  * If it ever happens, we have nothing to fall back to, so we throw an error.
  * Should only be used for values that are required for further calculation.
  */
-function resolveOptionalOrThrow<T>(value: T | undefined, error?: Error): T {
-  if (value === undefined) {
+function resolveOptionalOrThrow<T>(value: T | undefined | null, error?: Error): T {
+  if (value === undefined || value === null) {
     throw error
       ? error
       : new Error("Could not resolve data. Value needed for further calculation is undefined.");
diff --git a/apps/taxes/src/modules/taxes/tax-provider-webhook.ts b/apps/taxes/src/modules/taxes/tax-provider-webhook.ts
index e942722..8a4d070 100644
--- a/apps/taxes/src/modules/taxes/tax-provider-webhook.ts
+++ b/apps/taxes/src/modules/taxes/tax-provider-webhook.ts
@@ -1,10 +1,10 @@
 import { SyncWebhookResponsesMap } from "@saleor/app-sdk/handlers/next";
 import {
-  OrderCancelledEventSubscriptionFragment,
   OrderCreatedSubscriptionFragment,
   OrderFulfilledSubscriptionFragment,
   TaxBaseFragment,
 } from "../../../generated/graphql";
+import { OrderCancelledPayload } from "../../pages/api/webhooks/order-cancelled";
 
 export type CalculateTaxesResponse = SyncWebhookResponsesMap["ORDER_CALCULATE_TAXES"];
 
@@ -14,5 +14,5 @@ export interface ProviderWebhookService {
   calculateTaxes: (payload: TaxBaseFragment) => Promise<CalculateTaxesResponse>;
   createOrder: (payload: OrderCreatedSubscriptionFragment) => Promise<CreateOrderResponse>;
   fulfillOrder: (payload: OrderFulfilledSubscriptionFragment) => Promise<{ ok: boolean }>;
-  cancelOrder: (payload: OrderCancelledEventSubscriptionFragment) => Promise<any>;
+  cancelOrder: (payload: OrderCancelledPayload) => Promise<void>;
 }
diff --git a/apps/taxes/src/modules/taxjar/taxjar-webhook.service.ts b/apps/taxes/src/modules/taxjar/taxjar-webhook.service.ts
index dfb1ac3..320aa48 100644
--- a/apps/taxes/src/modules/taxjar/taxjar-webhook.service.ts
+++ b/apps/taxes/src/modules/taxjar/taxjar-webhook.service.ts
@@ -50,6 +50,5 @@ export class TaxJarWebhookService implements ProviderWebhookService {
   async cancelOrder(payload: OrderCancelledEventSubscriptionFragment) {
     // todo: implement
     this.logger.debug("cancelOrder", payload);
-    return { ok: true };
   }
 }
diff --git a/apps/taxes/src/pages/api/webhooks/order-cancelled.ts b/apps/taxes/src/pages/api/webhooks/order-cancelled.ts
index c9f0186..184b6d9 100644
--- a/apps/taxes/src/pages/api/webhooks/order-cancelled.ts
+++ b/apps/taxes/src/pages/api/webhooks/order-cancelled.ts
@@ -13,7 +13,7 @@ export const config = {
   },
 };
 
-type OrderCancelledPayload = Extract<
+export type OrderCancelledPayload = Extract<
   OrderCancelledEventSubscriptionFragment,
   { __typename: "OrderCancelled" }
 >;