diff --git a/app/routes/expenses/$expenseId/edit.tsx b/app/routes/expenses/$expenseId/edit.tsx
new file mode 100644
index 0000000..9fde247
--- /dev/null
+++ b/app/routes/expenses/$expenseId/edit.tsx
@@ -0,0 +1,255 @@
+import { Expense } from "@prisma/client";
+import type { ActionFunction, LoaderFunction } from "remix";
+import {
+  useActionData,
+  redirect,
+  json,
+  useCatch,
+  Link,
+  Form,
+  useTransition,
+  useLoaderData,
+} from "remix";
+import { db } from "~/utils/db.server";
+import { requireUserId, getUser } from "~/utils/session.server";
+
+function validateExpenseDescription(description: string) {
+  if (description.length < 2) {
+    return `That expense's description is too short`;
+  }
+}
+
+type ActionData = {
+  formError?: string;
+  fieldErrors?: {
+    description: string | undefined;
+    amount?: string | undefined;
+    user?: string | undefined;
+  };
+  fields?: {
+    description: string;
+    amount: number;
+  };
+};
+
+type LoaderData = {
+  userId: string;
+  expense: Expense;
+};
+
+const badRequest = (data: ActionData) => json(data, { status: 400 });
+
+export const loader: LoaderFunction = async ({ request, params }) => {
+  const userId = await requireUserId(request);
+  if (!userId) {
+    throw new Response("Unauthorized", { status: 401 });
+  }
+
+  const expense = await db.expense.findUnique({
+    where: { id: params.expenseId },
+  });
+  if (!expense) {
+    throw new Response("What an expense! Not found.", { status: 404 });
+  }
+
+  const data: LoaderData = { userId, expense };
+  return data;
+};
+
+export const action: ActionFunction = async ({ request }) => {
+  const userId = await requireUserId(request);
+  const user = await getUser(request);
+  const form = await request.formData();
+  const description = form.get("description");
+  const amount = parseInt(form.get("amount")?.toString() || "0", 10);
+  if (
+    typeof description !== "string" ||
+    typeof amount !== "number" ||
+    user === null
+  ) {
+    return badRequest({
+      formError: `Form not submitted correctly.`,
+    });
+  }
+
+  const fieldErrors = {
+    description: validateExpenseDescription(description),
+  };
+  const fields = { description, amount };
+  if (Object.values(fieldErrors).some(Boolean)) {
+    return badRequest({ fieldErrors, fields });
+  }
+
+  const expense = await db.expense.create({
+    data: { ...fields, userId: userId, teamId: user.teamId },
+  });
+  if (!expense) {
+    return badRequest({
+      formError: `Could not create expense.`,
+    });
+  }
+  return redirect(`/expenses/${expense.id}`);
+};
+
+export default function EditExpenseRoute() {
+  const data = useLoaderData<LoaderData>();
+  const actionData = useActionData<ActionData>();
+  const transition = useTransition();
+
+  if (transition.submission) {
+    const description = transition.submission.formData.get("description");
+    const amount = transition.submission.formData.get("content");
+    if (
+      typeof description === "string" &&
+      typeof amount === "number" &&
+      !validateExpenseDescription(description)
+    ) {
+      return (
+        <div>
+          <p>Description: {description}</p>
+          <p>Amount: {amount}€</p>
+          <p>User: {data.userId}</p>
+        </div>
+      );
+    }
+  }
+
+  return (
+    <>
+      <div className="container mx-auto min-h-full flex items-center justify-center py-12 px-4 sm:px-6 lg:px-8">
+        <div className="card bg-base-200 w-full shadow-lg max-w-lg">
+          <div className="card-body w-full">
+            <h1 className="card-title">Edit expense</h1>
+            <Form
+              method="post"
+              className="mt-5"
+              aria-describedby={
+                actionData?.formError ? "form-error-message" : undefined
+              }
+            >
+              <div className="form-control mb-3">
+                <label className="label" htmlFor="description-input">
+                  <span className="label-text">Description</span>
+                </label>
+                <input
+                  type="text"
+                  className="input input-bordered"
+                  name="description"
+                  id="description-input"
+                  defaultValue={
+                    actionData?.fields?.description ?? data.expense.description
+                  }
+                  aria-invalid={
+                    Boolean(actionData?.fieldErrors?.description) || undefined
+                  }
+                  aria-describedby={
+                    actionData?.fieldErrors?.description
+                      ? "description-error"
+                      : undefined
+                  }
+                />
+                {actionData?.fieldErrors?.description && (
+                  <div className="alert alert-error mt-3" role="alert">
+                    <div className="flex-1">
+                      <svg
+                        xmlns="http://www.w3.org/2000/svg"
+                        fill="none"
+                        viewBox="0 0 24 24"
+                        className="w-6 h-6 mx-2 stroke-current"
+                      >
+                        <path
+                          strokeLinecap="round"
+                          strokeLinejoin="round"
+                          strokeWidth="2"
+                          d="M18.364 18.364A9 9 0 005.636 5.636m12.728 12.728A9 9 0 015.636 5.636m12.728 12.728L5.636 5.636"
+                        ></path>
+                      </svg>
+                      <label id="description-error">
+                        {actionData?.fieldErrors.description}
+                      </label>
+                    </div>
+                  </div>
+                )}
+              </div>
+              <div className="form-control mb-3">
+                <label className="label" htmlFor="amount-input">
+                  <span className="label-text">Amount</span>
+                </label>
+                <input
+                  type="number"
+                  className="input input-bordered"
+                  id="amount-input"
+                  name="amount"
+                  defaultValue={
+                    actionData?.fields?.amount ?? data.expense.amount
+                  }
+                />
+              </div>
+              {actionData?.formError && (
+                <div className="alert alert-error mt-5" role="alert">
+                  <div className="flex-1">
+                    <svg
+                      xmlns="http://www.w3.org/2000/svg"
+                      fill="none"
+                      viewBox="0 0 24 24"
+                      className="w-6 h-6 mx-2 stroke-current"
+                    >
+                      <path
+                        strokeLinecap="round"
+                        strokeLinejoin="round"
+                        strokeWidth="2"
+                        d="M18.364 18.364A9 9 0 005.636 5.636m12.728 12.728A9 9 0 015.636 5.636m12.728 12.728L5.636 5.636"
+                      ></path>
+                    </svg>
+                    <label id="form-error-message">
+                      {actionData?.formError}
+                    </label>
+                  </div>
+                </div>
+              )}
+              <div className="text-center max-w-xs mx-auto mt-10">
+                <button type="submit" className="btn btn-primary btn-block">
+                  Save
+                </button>
+              </div>
+            </Form>
+          </div>
+        </div>
+      </div>
+      <ul
+        className="menu px-3 menu-horizontal rounded-box max-w-xs mx-auto flex items-center justify-evenly"
+        role="navigation"
+      >
+        <li>
+          <Link
+            to={`/expenses/${data.expense.id}`}
+            className="btn btn-outline btn-accent"
+          >
+            Back
+          </Link>
+        </li>
+      </ul>
+    </>
+  );
+}
+
+export function CatchBoundary() {
+  const caught = useCatch();
+
+  if (caught.status === 401) {
+    return (
+      <div className="error-container">
+        <p>You must be logged in to submit an expense.</p>
+        <Link to="/login">Login</Link>
+      </div>
+    );
+  }
+}
+
+export function ErrorBoundary() {
+  return (
+    <div className="error-container">
+      Something unexpected went wrong. Sorry about that.
+    </div>
+  );
+}
diff --git a/app/routes/expenses/$expenseId.tsx b/app/routes/expenses/$expenseId/index.tsx
similarity index 96%
rename from app/routes/expenses/$expenseId.tsx
rename to app/routes/expenses/$expenseId/index.tsx
index ae8164c..39e3804 100644
--- a/app/routes/expenses/$expenseId.tsx
+++ b/app/routes/expenses/$expenseId/index.tsx
@@ -134,11 +134,17 @@ export default function ExpenseRoute() {
         {data.isOwner && (
           <>
             <div className="flex justify-center align-center mt-6">
+              <Link
+                to={`/expenses/${data.expense.id}/edit`}
+                className="btn btn-default mr-4"
+              >
+                Edit
+              </Link>
               <label
                 htmlFor="delete-expense-modal"
                 className="btn btn-error modal-button"
               >
-                Delete expense
+                Delete
               </label>
             </div>
             <input
diff --git a/app/routes/expenses/new.tsx b/app/routes/expenses/new.tsx
index 19e847a..a89ef37 100644
--- a/app/routes/expenses/new.tsx
+++ b/app/routes/expenses/new.tsx
@@ -202,7 +202,10 @@ export default function NewExpenseRoute() {
           </div>
         </div>
       </div>
-      <ul className="menu px-3 menu-horizontal rounded-box max-w-xs mx-auto flex items-center justify-evenly">
+      <ul
+        className="menu px-3 menu-horizontal rounded-box max-w-xs mx-auto flex items-center justify-evenly"
+        role="navigation"
+      >
         <li>
           <Link to="/expenses" className="btn btn-outline btn-accent">
             Back
diff --git a/app/routes/expenses/transfer.tsx b/app/routes/expenses/transfer.tsx
index a716c8f..567f23e 100644
--- a/app/routes/expenses/transfer.tsx
+++ b/app/routes/expenses/transfer.tsx
@@ -86,6 +86,10 @@ export const action: ActionFunction = async ({ request }) => {
       teamId: user.teamId,
     },
   });
+
+  if (!expenseFrom || !expenseTo)
+    return json("Internal Server Error", { status: 500 });
+
   return redirect(`/expenses`);
 };
 
@@ -181,7 +185,10 @@ export default function NewExpenseRoute() {
           </div>
         </div>
       </div>
-      <ul className="menu px-3 menu-horizontal rounded-box max-w-xs mx-auto flex items-center justify-evenly">
+      <ul
+        className="menu px-3 menu-horizontal rounded-box max-w-xs mx-auto flex items-center justify-evenly"
+        role="navigation"
+      >
         <li>
           <Link to="/expenses" className="btn btn-outline btn-accent">
             Back