diff --git a/apps/dashboard/app/members/page.tsx b/apps/dashboard/app/members/page.tsx
index dfd0bee..11e55ed 100644
--- a/apps/dashboard/app/members/page.tsx
+++ b/apps/dashboard/app/members/page.tsx
@@ -8,6 +8,7 @@ import StatusBadge from "@/components/StatusBadge";
 import WalletAddressText from "@/components/WalletAddressText";
 import UnsupportedBanner from "@/components/UnsupportedBanner";
 import { ApiClientError, readApiResult } from "@/lib/api-client";
+import { tryNormaliseAddress } from "@/lib/address";
 import { getClientApiMode } from "@/lib/client-env";
 import { useSession } from "@/lib/hooks/useSession";
 import { useOptimisticMutation } from "@/lib/hooks/useOptimisticMutation";
@@ -101,6 +102,7 @@ function MembersPageContent() {
   const [isInviteOpen, setIsInviteOpen] = useState(false);
   const [inviteLoading, setInviteLoading] = useState(false);
   const [form, setForm] = useState({ name: "", wallet: "" });
+  const [walletError, setWalletError] = useState<string | null>(null);
 
   const updateFilterQuery = useCallback(
     (updates: { search?: string; status?: MemberStatusFilter; role?: MemberRoleFilter; guild?: string; page?: number | null }) => {
@@ -477,10 +479,33 @@ function MembersPageContent() {
             <h2 className="mb-4 text-lg font-semibold text-slate-900">Invite Member</h2>
             <div className="space-y-3">
               <input placeholder="Name" value={form.name} onChange={(e) => setForm({ ...form, name: e.target.value })} className="w-full rounded-lg border border-slate-200 p-2" />
-              <input placeholder="Wallet" value={form.wallet} onChange={(e) => setForm({ ...form, wallet: e.target.value })} className="w-full rounded-lg border border-slate-200 p-2" />
+              <div>
+                <input
+                  placeholder="Wallet"
+                  value={form.wallet}
+                  onChange={(e) => {
+                    setForm({ ...form, wallet: e.target.value });
+                    if (walletError) setWalletError(null);
+                  }}
+                  aria-invalid={walletError ? true : undefined}
+                  aria-describedby={walletError ? "invite-wallet-error" : undefined}
+                  className={`w-full rounded-lg border p-2 ${walletError ? "border-red-400" : "border-slate-200"}`}
+                />
+                {walletError && (
+                  <p id="invite-wallet-error" className="mt-1 text-xs text-red-600">
+                    {walletError}
+                  </p>
+                )}
+              </div>
             </div>
             <div className="mt-5 flex justify-end gap-2">
-              <button onClick={() => setIsInviteOpen(false)} className="rounded-lg border border-slate-200 px-4 py-2 text-sm text-slate-700">
+              <button
+                onClick={() => {
+                  setIsInviteOpen(false);
+                  setWalletError(null);
+                }}
+                className="rounded-lg border border-slate-200 px-4 py-2 text-sm text-slate-700"
+              >
                 Cancel
               </button>
               <button
@@ -488,14 +513,20 @@ function MembersPageContent() {
                 className="rounded-lg bg-violet-600 px-4 py-2 text-sm font-medium text-white disabled:opacity-50"
                 onClick={async () => {
                   if (!form.name.trim()) return alert("Name is required");
-                  if (!form.wallet.trim()) return alert("Wallet is required");
+
+                  const normalizedWallet = tryNormaliseAddress(form.wallet);
+                  if (!normalizedWallet) {
+                    setWalletError("Enter a valid Ethereum wallet address (0x followed by 40 hex characters).");
+                    return;
+                  }
+                  setWalletError(null);
 
                   try {
                     setInviteLoading(true);
                     const res = await guildFetch("/api/members", guildId, {
                       method: "POST",
                       headers: { "Content-Type": "application/json" },
-                      body: JSON.stringify({ name: form.name.trim(), wallet: form.wallet.trim() }),
+                      body: JSON.stringify({ name: form.name.trim(), wallet: normalizedWallet }),
                     });
                     const newMember = await readApiResult<MockMember>(res);
                     const safeMember = {
@@ -509,7 +540,16 @@ function MembersPageContent() {
                     setIsInviteOpen(false);
                     setForm({ name: "", wallet: "" });
                   } catch (error: unknown) {
-                    alert(error instanceof Error ? error.message : "Failed to invite member.");
+                    const walletFieldError =
+                      error instanceof ApiClientError
+                        ? error.fields?.find((field) => field.field === "wallet")?.message
+                        : undefined;
+
+                    if (walletFieldError) {
+                      setWalletError(walletFieldError);
+                    } else {
+                      alert(error instanceof Error ? error.message : "Failed to invite member.");
+                    }
                   } finally {
                     setInviteLoading(false);
                   }
diff --git a/apps/dashboard/components/WalletAddressText.tsx b/apps/dashboard/components/WalletAddressText.tsx
index 1540edc..755607b 100644
--- a/apps/dashboard/components/WalletAddressText.tsx
+++ b/apps/dashboard/components/WalletAddressText.tsx
@@ -2,6 +2,7 @@
 
 import { useState } from "react";
 import { formatWalletAddress } from "@/lib/formatters/wallet";
+import { copyToClipboard } from "@/lib/clipboard";
 
 type WalletAddressTextProps = {
   address?: string | null;
@@ -23,12 +24,12 @@ export default function WalletAddressText({
   const truncated = formatWalletAddress(address, prefixLength, suffixLength);
 
   const handleCopy = async () => {
-    try {
-      await navigator.clipboard.writeText(address);
+    const success = await copyToClipboard(address);
+    if (success) {
       setCopied(true);
       window.setTimeout(() => setCopied(false), 1500);
-    } catch (error) {
-      console.warn("Failed to copy wallet address:", error);
+    } else {
+      console.warn("Failed to copy wallet address");
     }
   };
 
diff --git a/apps/dashboard/lib/address.ts b/apps/dashboard/lib/address.ts
index 58d5dba..51ecbe5 100644
--- a/apps/dashboard/lib/address.ts
+++ b/apps/dashboard/lib/address.ts
@@ -14,7 +14,26 @@ export function normaliseAddress(addr: string): string {
   return getAddress(addr);
 }
 
+/**
+ * Best-effort version of `normaliseAddress` for form inputs: trims whitespace
+ * and returns the checksummed address, or `null` if the value isn't a valid
+ * Ethereum address (never throws).
+ */
+export function tryNormaliseAddress(addr: string | null | undefined): string | null {
+  if (!addr || typeof addr !== "string") return null;
+
+  const trimmed = addr.trim();
+  if (!trimmed) return null;
+
+  try {
+    return getAddress(trimmed);
+  } catch {
+    return null;
+  }
+}
+
 export default {
   isValidChecksumAddress,
   normaliseAddress,
+  tryNormaliseAddress,
 };
diff --git a/apps/dashboard/lib/clipboard.ts b/apps/dashboard/lib/clipboard.ts
new file mode 100644
index 0000000..e09eb64
--- /dev/null
+++ b/apps/dashboard/lib/clipboard.ts
@@ -0,0 +1,9 @@
+/** Writes text to the clipboard, returning whether it succeeded (never throws). */
+export async function copyToClipboard(text: string): Promise<boolean> {
+  try {
+    await navigator.clipboard.writeText(text);
+    return true;
+  } catch {
+    return false;
+  }
+}
diff --git a/apps/dashboard/test/address.test.ts b/apps/dashboard/test/address.test.ts
new file mode 100644
index 0000000..942640f
--- /dev/null
+++ b/apps/dashboard/test/address.test.ts
@@ -0,0 +1,102 @@
+import { describe, test } from "node:test";
+import assert from "node:assert/strict";
+
+import { isValidChecksumAddress, normaliseAddress, tryNormaliseAddress } from "../lib/address";
+
+const CHECKSUMMED = "0x742d35cC6634c0532925a3B8879539d43374E290";
+const LOWERCASE = CHECKSUMMED.toLowerCase();
+const UPPERCASE = "0x" + CHECKSUMMED.slice(2).toUpperCase();
+const BAD_CHECKSUM = "0x742d35cc6634C0532925a3B8879539d43374E290"; // mixed case, wrong checksum
+const MALFORMED = "0x123456"; // too short
+const EMPTY = "";
+const WHITESPACE = "   ";
+
+describe("isValidChecksumAddress", () => {
+  test("accepts an already-checksummed address", () => {
+    assert.equal(isValidChecksumAddress(CHECKSUMMED), true);
+  });
+
+  test("rejects an all-lowercase address (not checksummed)", () => {
+    assert.equal(isValidChecksumAddress(LOWERCASE), false);
+  });
+
+  test("rejects an all-uppercase address (not checksummed)", () => {
+    assert.equal(isValidChecksumAddress(UPPERCASE), false);
+  });
+
+  test("rejects a mixed-case address with an incorrect checksum", () => {
+    assert.equal(isValidChecksumAddress(BAD_CHECKSUM), false);
+  });
+
+  test("rejects a malformed address", () => {
+    assert.equal(isValidChecksumAddress(MALFORMED), false);
+  });
+
+  test("rejects an empty string", () => {
+    assert.equal(isValidChecksumAddress(EMPTY), false);
+  });
+});
+
+describe("normaliseAddress", () => {
+  test("returns the checksummed form of a lowercase address", () => {
+    assert.equal(normaliseAddress(LOWERCASE), CHECKSUMMED);
+  });
+
+  test("returns the checksummed form of an uppercase address", () => {
+    assert.equal(normaliseAddress(UPPERCASE), CHECKSUMMED);
+  });
+
+  test("returns an already-checksummed address unchanged", () => {
+    assert.equal(normaliseAddress(CHECKSUMMED), CHECKSUMMED);
+  });
+
+  test("normalises a mixed-case address with an incorrect checksum to the canonical form", () => {
+    // getAddress recomputes the checksum from the underlying hex digits — it
+    // corrects bad casing rather than treating it as invalid. Only
+    // `isValidChecksumAddress` rejects non-canonical casing.
+    assert.equal(normaliseAddress(BAD_CHECKSUM), CHECKSUMMED);
+  });
+
+  test("throws for a malformed address", () => {
+    assert.throws(() => normaliseAddress(MALFORMED));
+  });
+});
+
+describe("tryNormaliseAddress", () => {
+  test("normalises a valid lowercase address", () => {
+    assert.equal(tryNormaliseAddress(LOWERCASE), CHECKSUMMED);
+  });
+
+  test("normalises a valid uppercase address", () => {
+    assert.equal(tryNormaliseAddress(UPPERCASE), CHECKSUMMED);
+  });
+
+  test("normalises an already-checksummed address", () => {
+    assert.equal(tryNormaliseAddress(CHECKSUMMED), CHECKSUMMED);
+  });
+
+  test("normalises a mixed-case address with an incorrect checksum to the canonical form", () => {
+    assert.equal(tryNormaliseAddress(BAD_CHECKSUM), CHECKSUMMED);
+  });
+
+  test("returns null for a malformed address", () => {
+    assert.equal(tryNormaliseAddress(MALFORMED), null);
+  });
+
+  test("returns null for an empty string", () => {
+    assert.equal(tryNormaliseAddress(EMPTY), null);
+  });
+
+  test("returns null for whitespace-only input", () => {
+    assert.equal(tryNormaliseAddress(WHITESPACE), null);
+  });
+
+  test("trims surrounding whitespace before normalising", () => {
+    assert.equal(tryNormaliseAddress(`  ${LOWERCASE}  `), CHECKSUMMED);
+  });
+
+  test("returns null for null or undefined input", () => {
+    assert.equal(tryNormaliseAddress(null), null);
+    assert.equal(tryNormaliseAddress(undefined), null);
+  });
+});
diff --git a/apps/dashboard/test/clipboard.test.ts b/apps/dashboard/test/clipboard.test.ts
new file mode 100644
index 0000000..f6f3a19
--- /dev/null
+++ b/apps/dashboard/test/clipboard.test.ts
@@ -0,0 +1,69 @@
+import { describe, test } from "node:test";
+import assert from "node:assert/strict";
+
+import { copyToClipboard } from "../lib/clipboard";
+
+const WALLET = "0x742d35cC6634c0532925a3B8879539d43374E290";
+
+/**
+ * `navigator` is a getter-only global in Node, so it must be overridden via
+ * `Object.defineProperty` (a plain assignment throws in strict-mode ESM).
+ */
+async function withStubbedNavigator<T>(stub: unknown, run: () => Promise<T>): Promise<T> {
+  const original = Object.getOwnPropertyDescriptor(globalThis, "navigator");
+
+  Object.defineProperty(globalThis, "navigator", {
+    value: stub,
+    configurable: true,
+    writable: true,
+  });
+
+  try {
+    return await run();
+  } finally {
+    if (original) {
+      Object.defineProperty(globalThis, "navigator", original);
+    }
+  }
+}
+
+describe("copyToClipboard", () => {
+  test("returns true and writes the given text when the clipboard API succeeds", async () => {
+    const written: string[] = [];
+
+    const result = await withStubbedNavigator(
+      {
+        clipboard: {
+          writeText: async (text: string) => {
+            written.push(text);
+          },
+        },
+      },
+      () => copyToClipboard(WALLET)
+    );
+
+    assert.equal(result, true);
+    assert.deepEqual(written, [WALLET]);
+  });
+
+  test("returns false when the clipboard API rejects", async () => {
+    const result = await withStubbedNavigator(
+      {
+        clipboard: {
+          writeText: async () => {
+            throw new Error("Clipboard permission denied");
+          },
+        },
+      },
+      () => copyToClipboard(WALLET)
+    );
+
+    assert.equal(result, false);
+  });
+
+  test("returns false when clipboard access is unavailable", async () => {
+    const result = await withStubbedNavigator({}, () => copyToClipboard(WALLET));
+
+    assert.equal(result, false);
+  });
+});