diff --git a/src/index.ts b/src/index.ts
index 85eae2a..87e66d5 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -531,7 +531,7 @@ export { watchContractUpgrade } from "./upgrade.js";
 
 export { calculateFee } from "./fee.js";
 
-export { formatAddress, parseAmount, formatAmount } from "./utils.js";
+export { formatAddress } from "./utils.js";
 
 export { resolveToken } from "./token.js";
 
@@ -1156,3 +1156,20 @@ export type { MemoryReport } from "./memoryOptimizer.js";
 // Streaming Datasets (#1139)
 export { StreamingDatasetIterator } from "./streamingDataset.js";
 export type { PageResult, StreamingDatasetOptions } from "./streamingDataset.js";
+
+// Invoice Reminder Scheduler (#616)
+export {
+  InvoiceReminderScheduler,
+  DEFAULT_GRACE_PERIOD_MS,
+  scheduleReminder,
+  cancelReminder,
+  getPendingReminders,
+  clearAllReminders,
+} from "./invoiceReminderScheduler.js";
+export type {
+  InvoiceReminderSchedulerEventMap,
+  InvoiceDueAtResolver,
+  InvoiceReminderSchedulerOptions,
+  PendingReminder,
+  ScheduleReminderOptions,
+} from "./invoiceReminderScheduler.js";
diff --git a/src/invoiceReminderScheduler.ts b/src/invoiceReminderScheduler.ts
index c70ac7e..1849d38 100644
--- a/src/invoiceReminderScheduler.ts
+++ b/src/invoiceReminderScheduler.ts
@@ -118,6 +118,44 @@ export class InvoiceReminderScheduler extends TypedEventEmitter<InvoiceReminderS
     this._persist();
   }
 
+  /**
+   * Cancel a single pending reminder by its unique reminder ID.
+   * Returns `true` if cancelled, or `false` if the ID is unknown or already fired/cancelled.
+   */
+  cancelReminder(reminderId: string): boolean {
+    const entry = this.schedules.find((s) => s.id === reminderId);
+    if (!entry || entry.status !== "pending") {
+      return false;
+    }
+
+    const timer = this.timers.get(reminderId);
+    if (timer !== undefined) clearTimeout(timer);
+    this.timers.delete(reminderId);
+
+    entry.status = "cancelled";
+    this._persist();
+    return true;
+  }
+
+  /** Return all not-yet-fired, not-cancelled reminders. */
+  getPendingReminders(): PendingReminder[] {
+    return this.schedules
+      .filter((s) => s.status === "pending")
+      .map((s) => ({
+        reminderId: s.id,
+        invoiceId: s.invoiceId,
+        remindAt: s.fireAt,
+      }));
+  }
+
+  /** Clear all reminders and stop all active timers for teardown. */
+  clearAllReminders(): void {
+    for (const timer of this.timers.values()) clearTimeout(timer);
+    this.timers.clear();
+    this.schedules = [];
+    this._persist();
+  }
+
   /** Return the current set of reminder schedules (all invoices, all statuses). */
   list(): ReminderSchedule[] {
     return [...this.schedules];
@@ -173,3 +211,121 @@ export class InvoiceReminderScheduler extends TypedEventEmitter<InvoiceReminderS
     saveReminderSchedules(this.schedules);
   }
 }
+
+/** Represents a pending reminder entry returned by {@link getPendingReminders}. */
+export interface PendingReminder {
+  reminderId: string;
+  invoiceId: string;
+  remindAt: number;
+}
+
+/** Options object accepted by {@link scheduleReminder}. */
+export interface ScheduleReminderOptions {
+  invoiceId: string;
+  remindAt: number | Date;
+  callback?: (invoiceId: string) => void;
+  onRemind?: (invoiceId: string) => void;
+}
+
+interface StandaloneReminderRecord extends PendingReminder {
+  status: "pending" | "fired" | "cancelled";
+  timer?: ReturnType<typeof setTimeout>;
+  callback?: (invoiceId: string) => void;
+}
+
+const standaloneReminders = new Map<string, StandaloneReminderRecord>();
+
+/**
+ * Schedule an invoice reminder to fire at `remindAt` (Unix timestamp in ms or `Date`).
+ *
+ * @returns An opaque unique `reminderId` string that can be passed to {@link cancelReminder}.
+ */
+export function scheduleReminder(
+  invoiceIdOrOptions: string | ScheduleReminderOptions,
+  remindAt?: number | Date,
+  callback?: (invoiceId: string) => void,
+): string {
+  const invoiceId =
+    typeof invoiceIdOrOptions === "string"
+      ? invoiceIdOrOptions
+      : invoiceIdOrOptions.invoiceId;
+  const rawRemindAt =
+    typeof invoiceIdOrOptions === "string"
+      ? remindAt!
+      : invoiceIdOrOptions.remindAt;
+  const cb =
+    typeof invoiceIdOrOptions === "string"
+      ? callback
+      : (invoiceIdOrOptions.callback ?? invoiceIdOrOptions.onRemind);
+
+  const remindAtMs =
+    rawRemindAt instanceof Date ? rawRemindAt.getTime() : Number(rawRemindAt);
+  const reminderId = randomUUID();
+  const delayMs = Math.max(0, remindAtMs - Date.now());
+
+  const record: StandaloneReminderRecord = {
+    reminderId,
+    invoiceId,
+    remindAt: remindAtMs,
+    status: "pending",
+    callback: cb,
+  };
+
+  record.timer = setTimeout(() => {
+    const current = standaloneReminders.get(reminderId);
+    if (!current || current.status !== "pending") return;
+    current.status = "fired";
+    current.timer = undefined;
+    current.callback?.(current.invoiceId);
+  }, delayMs);
+
+  standaloneReminders.set(reminderId, record);
+  return reminderId;
+}
+
+/**
+ * Cancel a scheduled reminder by its `reminderId`.
+ *
+ * @returns `true` if the reminder was pending and has been cancelled; `false` if the ID is unknown or already fired/cancelled.
+ */
+export function cancelReminder(reminderId: string): boolean {
+  const record = standaloneReminders.get(reminderId);
+  if (!record || record.status !== "pending") {
+    return false;
+  }
+  if (record.timer !== undefined) {
+    clearTimeout(record.timer);
+    record.timer = undefined;
+  }
+  record.status = "cancelled";
+  return true;
+}
+
+/**
+ * Return all not-yet-fired, not-cancelled reminders scheduled via {@link scheduleReminder}.
+ */
+export function getPendingReminders(): PendingReminder[] {
+  const pending: PendingReminder[] = [];
+  for (const record of standaloneReminders.values()) {
+    if (record.status === "pending") {
+      pending.push({
+        reminderId: record.reminderId,
+        invoiceId: record.invoiceId,
+        remindAt: record.remindAt,
+      });
+    }
+  }
+  return pending;
+}
+
+/**
+ * Clear all reminders and stop their timers (intended for test teardown).
+ */
+export function clearAllReminders(): void {
+  for (const record of standaloneReminders.values()) {
+    if (record.timer !== undefined) {
+      clearTimeout(record.timer);
+    }
+  }
+  standaloneReminders.clear();
+}
diff --git a/test/invoiceReminderScheduler.test.ts b/test/invoiceReminderScheduler.test.ts
index 8c53fcf..ffba9a8 100644
--- a/test/invoiceReminderScheduler.test.ts
+++ b/test/invoiceReminderScheduler.test.ts
@@ -2,7 +2,12 @@ import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
 import {
   InvoiceReminderScheduler,
   DEFAULT_GRACE_PERIOD_MS,
+  scheduleReminder,
+  cancelReminder,
+  getPendingReminders,
+  clearAllReminders,
 } from "../src/invoiceReminderScheduler.js";
+import * as sdkIndex from "../src/index.js";
 import { loadReminderSchedules } from "../src/snapshot.js";
 import type { ReminderEvent } from "../src/types.js";
 
@@ -152,4 +157,112 @@ describe("InvoiceReminderScheduler", () => {
     expect(events).toHaveLength(0);
     expect(scheduler.list()[0]!.status).toBe("expired");
   });
+
+  it("supports cancelReminder, getPendingReminders, and clearAllReminders on InvoiceReminderScheduler instance", async () => {
+    scheduler = new InvoiceReminderScheduler(() => DUE_AT);
+    const events: ReminderEvent[] = [];
+    scheduler.on("invoiceReminderDue", (e) => events.push(e));
+
+    const created = await scheduler.schedule(INVOICE_ID, [60 * 60 * 1000, 30 * 60 * 1000]);
+    expect(scheduler.getPendingReminders()).toHaveLength(2);
+
+    const firstId = created[0]!.id;
+    const secondId = created[1]!.id;
+    expect(scheduler.cancelReminder(firstId)).toBe(true);
+    expect(scheduler.cancelReminder(firstId)).toBe(false);
+    expect(scheduler.cancelReminder("unknown-id")).toBe(false);
+
+    const pending = scheduler.getPendingReminders();
+    expect(pending).toEqual([
+      {
+        reminderId: secondId,
+        invoiceId: INVOICE_ID,
+        remindAt: DUE_AT - 30 * 60 * 1000,
+      },
+    ]);
+
+    vi.advanceTimersByTime(24 * 60 * 60 * 1000 + 1);
+    expect(events).toHaveLength(1);
+    expect(events[0]!.offsetMs).toBe(30 * 60 * 1000);
+    expect(scheduler.cancelReminder(secondId)).toBe(false);
+
+    await scheduler.schedule("inv_456", [10 * 60 * 1000]);
+    expect(scheduler.getPendingReminders()).toHaveLength(1);
+    scheduler.clearAllReminders();
+    expect(scheduler.getPendingReminders()).toEqual([]);
+  });
+});
+
+describe("scheduleReminder / cancelReminder / getPendingReminders / clearAllReminders (#616)", () => {
+  beforeEach(() => {
+    clearAllReminders();
+    vi.useFakeTimers();
+    vi.setSystemTime(NOW);
+  });
+
+  afterEach(() => {
+    clearAllReminders();
+    vi.useRealTimers();
+  });
+
+  it("re-exports reminder helpers from src/index.ts", () => {
+    expect(typeof sdkIndex.scheduleReminder).toBe("function");
+    expect(typeof sdkIndex.cancelReminder).toBe("function");
+    expect(typeof sdkIndex.getPendingReminders).toBe("function");
+    expect(typeof sdkIndex.clearAllReminders).toBe("function");
+  });
+
+  it("cancelling before fire prevents callback execution and excludes it from getPendingReminders()", () => {
+    const callback = vi.fn();
+    const remindAt = NOW + 60_000;
+    const reminderId = scheduleReminder(INVOICE_ID, remindAt, callback);
+
+    expect(typeof reminderId).toBe("string");
+    expect(reminderId.length).toBeGreaterThan(0);
+    expect(getPendingReminders()).toEqual([
+      { reminderId, invoiceId: INVOICE_ID, remindAt },
+    ]);
+
+    expect(cancelReminder(reminderId)).toBe(true);
+    expect(getPendingReminders()).toEqual([]);
+
+    vi.advanceTimersByTime(120_000);
+    expect(callback).not.toHaveBeenCalled();
+  });
+
+  it("returns false when cancelling an unknown ID or an already-cancelled ID", () => {
+    const remindAt = NOW + 60_000;
+    const reminderId = scheduleReminder(INVOICE_ID, remindAt);
+
+    expect(cancelReminder("non-existent-id")).toBe(false);
+    expect(cancelReminder(reminderId)).toBe(true);
+    expect(cancelReminder(reminderId)).toBe(false);
+  });
+
+  it("returns false when cancelling an already-fired reminder and excludes fired reminders from getPendingReminders()", () => {
+    const callback = vi.fn();
+    const remindAt = NOW + 30_000;
+    const reminderId = scheduleReminder(INVOICE_ID, remindAt, callback);
+
+    vi.advanceTimersByTime(30_000);
+    expect(callback).toHaveBeenCalledTimes(1);
+    expect(callback).toHaveBeenCalledWith(INVOICE_ID);
+    expect(getPendingReminders()).toEqual([]);
+    expect(cancelReminder(reminderId)).toBe(false);
+  });
+
+  it("clearAllReminders() stops all pending timers and empties getPendingReminders()", () => {
+    const cb1 = vi.fn();
+    const cb2 = vi.fn();
+    scheduleReminder("inv_1", NOW + 10_000, cb1);
+    scheduleReminder({ invoiceId: "inv_2", remindAt: NOW + 20_000, callback: cb2 });
+
+    expect(getPendingReminders()).toHaveLength(2);
+    clearAllReminders();
+    expect(getPendingReminders()).toEqual([]);
+
+    vi.advanceTimersByTime(30_000);
+    expect(cb1).not.toHaveBeenCalled();
+    expect(cb2).not.toHaveBeenCalled();
+  });
 });