diff --git a/packages/api/src/router/stripe/index.ts b/packages/api/src/router/stripe/index.ts
index e9c34e430..c09b23b19 100644
--- a/packages/api/src/router/stripe/index.ts
+++ b/packages/api/src/router/stripe/index.ts
@@ -28,6 +28,7 @@ import { z } from "zod";
 import { createTRPCRouter, protectedProcedure } from "../../trpc";
 import {
   buildFromSubscriptionOrThrow,
+  canAutomateTax,
   getCurrentPeriodEnd,
   getCurrentSubscription,
   hasPaymentMethod,
@@ -104,6 +105,9 @@ async function createPaymentMethodSetupSession(args: {
     mode: "setup",
     payment_method_types: ["card"],
     customer: args.customer,
+    // The address lets Stripe Tax place the customer once the trial converts.
+    billing_address_collection: "required",
+    customer_update: { name: "auto", address: "auto" },
     setup_intent_data: { metadata: { subscriptionId: args.subscriptionId } },
     success_url: args.successUrl,
     cancel_url: args.cancelUrl,
@@ -262,6 +266,9 @@ export const stripeRouter = createTRPCRouter({
           items,
           proration_behavior: "create_prorations",
           cancel_at_period_end: false,
+          ...((await canAutomateTax(stripeId)) && {
+            automatic_tax: { enabled: true },
+          }),
           ...(isTrialing && {
             trial_end: "now",
             payment_behavior: "error_if_incomplete",
@@ -305,6 +312,8 @@ export const stripeRouter = createTRPCRouter({
           name: "auto",
           address: "auto",
         },
+        billing_address_collection: "required",
+        automatic_tax: { enabled: true },
         line_items: [
           {
             price: priceId,
diff --git a/packages/api/src/router/stripe/shared.ts b/packages/api/src/router/stripe/shared.ts
index fe325152e..e6ccf88bf 100644
--- a/packages/api/src/router/stripe/shared.ts
+++ b/packages/api/src/router/stripe/shared.ts
@@ -194,6 +194,18 @@ export async function hasPaymentMethod(subscription: Stripe.Subscription) {
   );
 }
 
+// Stripe rejects automatic tax on a subscription whose customer it cannot
+// place (no address yet, e.g. a card-less trial), so only opt in once it can.
+// `not_collecting` is a valid location where we are not registered: no tax.
+export async function canAutomateTax(customerId: string) {
+  const customer = await stripe.customers.retrieve(customerId, {
+    expand: ["tax"],
+  });
+  if (customer.deleted) return false;
+  const status = customer.tax?.automatic_tax;
+  return status === "supported" || status === "not_collecting";
+}
+
 export function trialEndsAtOf(subscription: Stripe.Subscription) {
   return subscription.status === "trialing" && subscription.trial_end
     ? new Date(subscription.trial_end * 1000)
diff --git a/packages/api/src/router/stripe/trial-lifecycle.test.ts b/packages/api/src/router/stripe/trial-lifecycle.test.ts
index e919d2fbf..f5a9b82b5 100644
--- a/packages/api/src/router/stripe/trial-lifecycle.test.ts
+++ b/packages/api/src/router/stripe/trial-lifecycle.test.ts
@@ -454,6 +454,68 @@ describe("trial lifecycle", () => {
       ]);
     });
 
+    function stubSetup() {
+      stubs.push(
+        stub(stripe.setupIntents, "retrieve", () =>
+          Promise.resolve({
+            payment_method: "pm_new",
+            metadata: { subscriptionId: "sub_setup" },
+          } as unknown as Stripe.Response<Stripe.SetupIntent>),
+        ),
+        stub(stripe.subscriptions, "retrieve", () =>
+          Promise.resolve(
+            subscription("cus_setup", {
+              id: "sub_setup",
+            }) as Stripe.Response<Stripe.Subscription>,
+          ),
+        ),
+        stub(stripe.customers, "update", () =>
+          Promise.resolve({} as Stripe.Response<Stripe.Customer>),
+        ),
+      );
+    }
+
+    const setupCompleted = () =>
+      event("checkout.session.completed", {
+        mode: "setup",
+        customer: "cus_setup",
+        setup_intent: "seti_1",
+      } as Stripe.Checkout.Session);
+
+    test("setup checkout completed → automatic tax on after the card", async () => {
+      stubSetup();
+
+      await caller().sessionCompleted(setupCompleted());
+
+      expect(updateSubscription.calls.map((c) => c.args)).toEqual([
+        ["sub_setup", { default_payment_method: "pm_new" }],
+        ["sub_setup", { automatic_tax: { enabled: true } }],
+      ]);
+    });
+
+    test("Stripe rejecting the tax location still keeps the card", async () => {
+      stubSetup();
+      stubs = stubs.filter((s) => s !== updateSubscription);
+      updateSubscription.restore();
+      const update = stub(
+        stripe.subscriptions,
+        "update",
+        (_id: string, params?: Stripe.SubscriptionUpdateParams) =>
+          params?.automatic_tax
+            ? Promise.reject(new Error("customer_tax_location_invalid"))
+            : Promise.resolve({} as Stripe.Response<Stripe.Subscription>),
+      );
+      stubs.push(update);
+
+      await caller().sessionCompleted(setupCompleted());
+
+      expect(update.calls[0]?.args).toEqual([
+        "sub_setup",
+        { default_payment_method: "pm_new" },
+      ]);
+      assertSpyCalls(update, 2);
+    });
+
     test("trialing → active clears trialEndsAt", async () => {
       const s = await seedTrial();
       const sub = subscription(s.stripeId, { status: "active" });
diff --git a/packages/api/src/router/stripe/webhook.ts b/packages/api/src/router/stripe/webhook.ts
index 7ffe3b095..486f39716 100644
--- a/packages/api/src/router/stripe/webhook.ts
+++ b/packages/api/src/router/stripe/webhook.ts
@@ -224,6 +224,22 @@ async function attachSetupPaymentMethod(session: Stripe.Checkout.Session) {
   await stripe.subscriptions.update(subscriptionId, {
     default_payment_method: paymentMethod,
   });
+
+  // The card now carries the billing address the setup session required, and
+  // Stripe Tax falls back to it. Just try: Stripe rejects a location it cannot
+  // place, and that must not undo the card we already attached.
+  if (!subscription.automatic_tax?.enabled) {
+    try {
+      await stripe.subscriptions.update(subscriptionId, {
+        automatic_tax: { enabled: true },
+      });
+    } catch (err) {
+      console.error(
+        `Failed to enable automatic tax on ${subscriptionId}:`,
+        err,
+      );
+    }
+  }
   return subscription;
 }