diff --git a/.changeset/payment-option-empty-fields.md b/.changeset/payment-option-empty-fields.md
new file mode 100644
index 00000000..ca60103f
--- /dev/null
+++ b/.changeset/payment-option-empty-fields.md
@@ -0,0 +1,10 @@
+---
+"@agentcommercekit/ack-pay": patch
+---
+
+Reject empty payment request and payment option identifiers.
+
+`paymentOptionSchema` accepted empty strings for `id`, `currency`, and
+`recipient`, and `paymentRequestSchema` accepted an empty request `id`, even
+though other fields such as `amount` already reject invalid values. Require a
+non-empty string for these fields in both the valibot and zod schemas.
diff --git a/packages/ack-pay/src/schemas.test.ts b/packages/ack-pay/src/schemas.test.ts
index 802b45c8..baf38667 100644
--- a/packages/ack-pay/src/schemas.test.ts
+++ b/packages/ack-pay/src/schemas.test.ts
@@ -1,8 +1,14 @@
 import * as v from "valibot"
 import { describe, expect, it } from "vitest"
 
-import { paymentRequestSchema as valibotPaymentRequestSchema } from "./schemas/valibot"
-import { paymentRequestSchema as zodPaymentRequestSchema } from "./schemas/zod"
+import {
+  paymentOptionSchema as valibotPaymentOptionSchema,
+  paymentRequestSchema as valibotPaymentRequestSchema,
+} from "./schemas/valibot"
+import {
+  paymentOptionSchema as zodPaymentOptionSchema,
+  paymentRequestSchema as zodPaymentRequestSchema,
+} from "./schemas/zod"
 
 const paymentRequest = {
   id: "test-payment-request-id",
@@ -17,6 +23,46 @@ const paymentRequest = {
   ],
 }
 
+const paymentOption = paymentRequest.paymentOptions[0]
+
+const validators = {
+  valibot: {
+    paymentRequest: (input: unknown) =>
+      v.safeParse(valibotPaymentRequestSchema, input).success,
+    paymentOption: (input: unknown) =>
+      v.safeParse(valibotPaymentOptionSchema, input).success,
+  },
+  zod: {
+    paymentRequest: (input: unknown) =>
+      zodPaymentRequestSchema.safeParse(input).success,
+    paymentOption: (input: unknown) =>
+      zodPaymentOptionSchema.safeParse(input).success,
+  },
+} as const
+
+describe.each(Object.entries(validators))("%s payment schemas", (_, schema) => {
+  it.each(["id", "currency", "recipient"] as const)(
+    "rejects a payment option with an empty %s",
+    (field) => {
+      expect(
+        schema.paymentOption({
+          ...paymentOption,
+          [field]: "",
+        }),
+      ).toBe(false)
+    },
+  )
+
+  it("rejects a payment request with an empty id", () => {
+    expect(
+      schema.paymentRequest({
+        ...paymentRequest,
+        id: "",
+      }),
+    ).toBe(false)
+  })
+})
+
 describe("paymentRequestSchema", () => {
   it("rejects invalid expiresAt strings instead of throwing", () => {
     const input = {
diff --git a/packages/ack-pay/src/schemas/valibot.ts b/packages/ack-pay/src/schemas/valibot.ts
index d97ed94d..e2c43c34 100644
--- a/packages/ack-pay/src/schemas/valibot.ts
+++ b/packages/ack-pay/src/schemas/valibot.ts
@@ -4,6 +4,8 @@ import * as v from "valibot"
 
 const urlOrDidUri = v.union([v.pipe(v.string(), v.url()), didUriSchema])
 
+const nonEmptyString = v.pipe(v.string(), v.minLength(1))
+
 const timestampSchema = v.pipe(
   v.union([v.date(), v.string()]),
   v.check((input) => !Number.isNaN(new Date(input).getTime()), "Invalid date"),
@@ -11,18 +13,18 @@ const timestampSchema = v.pipe(
 )
 
 export const paymentOptionSchema = v.object({
-  id: v.string(),
+  id: nonEmptyString,
   amount: v.union([v.pipe(v.number(), v.integer(), v.gtValue(0)), v.string()]),
   decimals: v.pipe(v.number(), v.integer(), v.toMinValue(0)),
-  currency: v.string(),
-  recipient: v.string(),
+  currency: nonEmptyString,
+  recipient: nonEmptyString,
   network: v.optional(v.string()),
   paymentService: v.optional(urlOrDidUri),
   receiptService: v.optional(urlOrDidUri),
 })
 
 export const paymentRequestSchema = v.object({
-  id: v.string(),
+  id: nonEmptyString,
   description: v.optional(v.string()),
   serviceCallback: v.optional(v.pipe(v.string(), v.url())),
   expiresAt: v.optional(timestampSchema),
diff --git a/packages/ack-pay/src/schemas/zod.ts b/packages/ack-pay/src/schemas/zod.ts
index 0f676fcb..e6b77031 100644
--- a/packages/ack-pay/src/schemas/zod.ts
+++ b/packages/ack-pay/src/schemas/zod.ts
@@ -4,6 +4,8 @@ import * as z from "zod"
 
 const urlOrDidUri = z.union([z.url(), didUriSchema])
 
+const nonEmptyString = z.string().min(1)
+
 const timestampSchema = z
   .union([z.date(), z.string()])
   .transform((val, ctx) => {
@@ -21,18 +23,18 @@ const timestampSchema = z
   })
 
 export const paymentOptionSchema = z.object({
-  id: z.string(),
+  id: nonEmptyString,
   amount: z.union([z.number().int().positive(), z.string()]),
   decimals: z.number().int().nonnegative(),
-  currency: z.string(),
-  recipient: z.string(),
+  currency: nonEmptyString,
+  recipient: nonEmptyString,
   network: z.string().optional(),
   paymentService: urlOrDidUri.optional(),
   receiptService: urlOrDidUri.optional(),
 })
 
 export const paymentRequestSchema = z.object({
-  id: z.string(),
+  id: nonEmptyString,
   description: z.string().optional(),
   serviceCallback: z.url().optional(),
   expiresAt: timestampSchema.optional(),