diff --git a/README.md b/README.md
index a0c6e14..46c98d7 100644
--- a/README.md
+++ b/README.md
@@ -37,6 +37,7 @@ The following changes are already implemented:
 * [Federation page improvements](https://github.com/Awesome-Technologies/synapse-admin/pull/583) (using theme colors)
 * [Add UI option to block deleted rooms from being rejoined](https://github.com/etkecc/synapse-admin/pull/26)
 * [Fix required fields check on Bulk registration CSV upload](https://github.com/etkecc/synapse-admin/pull/32)
+* [Fix requests with invalid MXIDs on Bulk registration](https://github.com/etkecc/synapse-admin/pull/33)
 
 _the list will be updated as new changes are added_
 
diff --git a/src/components/ImportFeature.tsx b/src/components/ImportFeature.tsx
index ebd9b0f..3407fda 100644
--- a/src/components/ImportFeature.tsx
+++ b/src/components/ImportFeature.tsx
@@ -15,7 +15,7 @@ import {
 import { DataProvider, useTranslate } from "ra-core";
 import { useDataProvider, useNotify, RaRecord, Title } from "react-admin";
 
-import { generateRandomMxId, generateRandomPassword } from "../synapse/synapse";
+import { generateRandomMxId, generateRandomPassword, returnMXID } from "../synapse/synapse";
 
 const LOGGING = true;
 
@@ -74,7 +74,7 @@ const FilePicker = () => {
 
   const [conflictMode, setConflictMode] = useState("stop");
   const [passwordMode, setPasswordMode] = useState(true);
-  const [useridMode, setUseridMode] = useState("ignore");
+  const [useridMode, setUseridMode] = useState("update");
 
   const translate = useTranslate();
   const notify = useNotify();
@@ -266,12 +266,15 @@ const FilePicker = () => {
         const userRecord = { ...entry };
         // No need to do a bunch of cryptographic random number getting if
         // we are using neither a generated password nor a generated user id.
-        if (useridMode === "ignore" || userRecord.id === undefined) {
+        if (useridMode === "ignore" || userRecord.id === undefined || userRecord.id === "") {
           userRecord.id = generateRandomMxId();
         }
-        if (passwordMode === false || entry.password === undefined) {
+        if (passwordMode === false || entry.password === undefined || entry.password === "") {
           userRecord.password = generateRandomPassword();
         }
+        // we want to ensure that the ID is always full MXID, otherwise randomly-generated MXIDs will be in the full
+        // form, but the ones from the CSV will be localpart-only.
+        userRecord.id = returnMXID(userRecord.id);
         /* TODO record update stats (especially admin no -> yes, deactivated x -> !x, ... */
 
         /* For these modes we will consider the ID that's in the record.
diff --git a/src/synapse/dataProvider.ts b/src/synapse/dataProvider.ts
index d69a760..ada0b91 100644
--- a/src/synapse/dataProvider.ts
+++ b/src/synapse/dataProvider.ts
@@ -3,6 +3,7 @@ import { stringify } from "query-string";
 import { DataProvider, DeleteParams, HttpError, Identifier, Options, RaRecord, fetchUtils } from "react-admin";
 
 import storage from "../storage";
+import { returnMXID } from "./synapse.ts"
 import { MatrixError, displayError } from "../components/error";
 
 // Adds the access token to all requests
@@ -234,7 +235,7 @@ const resourceMap = {
     path: "/_synapse/admin/v2/users",
     map: (u: User) => ({
       ...u,
-      id: u.name,
+      id: returnMXID(u.name),
       avatar_src: u.avatar_url ? mxcUrlToHttp(u.avatar_url) : undefined,
       is_guest: !!u.is_guest,
       admin: !!u.admin,
@@ -245,12 +246,12 @@ const resourceMap = {
     data: "users",
     total: json => json.total,
     create: (data: RaRecord) => ({
-      endpoint: `/_synapse/admin/v2/users/@${encodeURIComponent(data.id)}:${storage.getItem("home_server")}`,
+      endpoint: `/_synapse/admin/v2/users/${encodeURIComponent(returnMXID(data.id))}`,
       body: data,
       method: "PUT",
     }),
     delete: (params: DeleteParams) => ({
-      endpoint: `/_synapse/admin/v1/deactivate/${encodeURIComponent(params.id)}`,
+      endpoint: `/_synapse/admin/v1/deactivate/${encodeURIComponent(returnMXID(params.id))}`,
       body: { erase: true },
       method: "POST",
     }),
@@ -349,7 +350,7 @@ const resourceMap = {
       id: um.media_id,
     }),
     reference: (id: Identifier) => ({
-      endpoint: `/_synapse/admin/v1/users/${encodeURIComponent(id)}/media`,
+      endpoint: `/_synapse/admin/v1/users/${encodeURIComponent(returnMXID(id))}/media`,
     }),
     data: "media",
     total: json => json.total,
@@ -384,7 +385,7 @@ const resourceMap = {
     create: (data: RaServerNotice) => ({
       endpoint: "/_synapse/admin/v1/send_server_notice",
       body: {
-        user_id: data.id,
+        user_id: returnMXID(data.id),
         content: {
           msgtype: "m.text",
           body: data.body,
@@ -397,7 +398,7 @@ const resourceMap = {
     path: "/_synapse/admin/v1/statistics/users/media",
     map: (usms: UserMediaStatistic) => ({
       ...usms,
-      id: usms.user_id,
+      id: returnMXID(usms.user_id),
     }),
     data: "users",
     total: json => json.total,
diff --git a/src/synapse/synapse.ts b/src/synapse/synapse.ts
index 3180fb9..13c18f3 100644
--- a/src/synapse/synapse.ts
+++ b/src/synapse/synapse.ts
@@ -72,6 +72,26 @@ export function generateRandomMxId(): string {
   return `@${localpart}:${homeserver}`;
 }
 
+/**
+ * Return the full MXID from an arbitrary input
+ * @param input  the input string
+ * @returns full MXID as string
+ */
+export function returnMXID(input: string): string {
+  const homeserver = storage.getItem("home_server");
+
+  // Check if the input already looks like a valid MXID (i.e., starts with "@" and contains ":")
+  const mxidPattern = /^@[^@:]+:[^@:]+$/;
+  if (mxidPattern.test(input)) {
+    return input; // Already a valid MXID
+  }
+
+  // If input is not a valid MXID, assume it's a localpart and construct the MXID
+  const localpart = input.startsWith('@') ? input.slice(1) : input;
+  return `@${localpart}:${homeserver}`;
+}
+
+
 /**
  * Generate a random user password
  * @returns a new random password as string