diff --git a/desktop/src/auto-update.js b/desktop/src/auto-update.js
--- a/desktop/src/auto-update.js
+++ b/desktop/src/auto-update.js
@@ -3,15 +3,15 @@
 // eslint-disable-next-line import/extensions
 import { app, ipcMain, autoUpdater } from 'electron/main';
 
-const getUpdateUrl = version =>
+const getUpdateURL = (version: string) =>
   `https://electron-update.commtechnologies.org/update/${process.platform}/${version}`;
 
 export function initAutoUpdate(): void {
-  autoUpdater.setFeedURL({ url: getUpdateUrl(app.getVersion()) });
+  autoUpdater.setFeedURL({ url: getUpdateURL(app.getVersion()) });
 
   // Check for new updates every 10 minutes
   const updateIntervalMs = 10 * 60_000;
-  let currentTimeout = null;
+  let currentTimeout: ?TimeoutID = null;
   const scheduleCheckForUpdates = () => {
     if (!currentTimeout) {
       currentTimeout = setTimeout(() => {
diff --git a/desktop/src/handle-squirrel-event.js b/desktop/src/handle-squirrel-event.js
--- a/desktop/src/handle-squirrel-event.js
+++ b/desktop/src/handle-squirrel-event.js
@@ -16,7 +16,7 @@
   const updateExe = path.resolve(process.execPath, '..', '..', 'Update.exe');
   const commExeName = path.basename(process.execPath);
 
-  const spawnUpdate = args => {
+  const spawnUpdate = (args: string[]) => {
     return spawn(updateExe, args, { detached: true }).on('close', app.quit);
   };
 
diff --git a/desktop/src/main.js b/desktop/src/main.js
--- a/desktop/src/main.js
+++ b/desktop/src/main.js
@@ -10,6 +10,7 @@
   autoUpdater,
   // eslint-disable-next-line import/extensions
 } from 'electron/main';
+import type { Event, MenuItemConstructorOptions } from 'electron';
 import contextMenu from 'electron-context-menu';
 import fs from 'fs';
 import path from 'path';
@@ -32,7 +33,7 @@
 
 let mainWindow = null;
 const setApplicationMenu = () => {
-  let mainMenu = [];
+  let mainMenu: MenuItemConstructorOptions[] = [];
   if (isMac) {
     mainMenu = [
       {
@@ -157,7 +158,11 @@
   };
   ipcMain.on('double-click-top-bar', doubleClickTopBar);
 
-  const updateDownloaded = (event, releaseNotes, releaseName) => {
+  const updateDownloaded = (
+    event: Event,
+    releaseNotes?: string,
+    releaseName: string,
+  ) => {
     win.webContents.send('on-new-version-available', releaseName);
   };
   autoUpdater.on('update-downloaded', updateDownloaded);
diff --git a/desktop/src/preload.js b/desktop/src/preload.js
--- a/desktop/src/preload.js
+++ b/desktop/src/preload.js
@@ -2,12 +2,16 @@
 
 // eslint-disable-next-line import/extensions
 import { contextBridge, ipcRenderer } from 'electron/renderer';
+import type { IpcRendererEvent } from 'electron';
 
 import type { ElectronBridge } from 'lib/types/electron-types.js';
 
 const bridge: ElectronBridge = {
   onNavigate: callback => {
-    const withEvent = (event, ...args) => callback(...args);
+    const withEvent = (
+      event: IpcRendererEvent,
+      ...args: $ReadOnlyArray<any>
+    ) => callback(...args);
     ipcRenderer.on('on-navigate', withEvent);
     return () => ipcRenderer.removeListener('on-navigate', withEvent);
   },
@@ -16,7 +20,10 @@
   setBadge: value => ipcRenderer.send('set-badge', value),
   version: ipcRenderer.sendSync('get-version'),
   onNewVersionAvailable: callback => {
-    const withEvent = (event, ...args) => callback(...args);
+    const withEvent = (
+      event: IpcRendererEvent,
+      ...args: $ReadOnlyArray<any>
+    ) => callback(...args);
     ipcRenderer.on('on-new-version-available', withEvent);
     return () =>
       ipcRenderer.removeListener('on-new-version-available', withEvent);
@@ -24,13 +31,19 @@
   updateToNewVersion: () => ipcRenderer.send('update-to-new-version'),
   platform: { win32: 'windows', darwin: 'macos' }[process.platform],
   onDeviceTokenRegistered: callback => {
-    const withEvent = (event, ...args) => callback(...args);
+    const withEvent = (
+      event: IpcRendererEvent,
+      ...args: $ReadOnlyArray<any>
+    ) => callback(...args);
     ipcRenderer.on('on-device-token-registered', withEvent);
     return () =>
       ipcRenderer.removeListener('on-device-token-registered', withEvent);
   },
   onNotificationClicked: callback => {
-    const withEvent = (event, ...args) => callback(...args);
+    const withEvent = (
+      event: IpcRendererEvent,
+      ...args: $ReadOnlyArray<any>
+    ) => callback(...args);
     ipcRenderer.on('on-notification-clicked', withEvent);
     return () =>
       ipcRenderer.removeListener('on-notification-clicked', withEvent);
diff --git a/desktop/src/push-notifications.js b/desktop/src/push-notifications.js
--- a/desktop/src/push-notifications.js
+++ b/desktop/src/push-notifications.js
@@ -1,5 +1,9 @@
 // @flow
 
+import type {
+  PushNotificationManager as PushNotificationManagerType,
+  PushNotificationReceivedEventArgs,
+} from '@commapp/windowspush';
 // eslint-disable-next-line import/extensions
 import { app, pushNotifications, Notification } from 'electron/main';
 import EventEmitter from 'events';
@@ -20,7 +24,10 @@
 
       windowsPushNotificationManager = PushNotificationManager.default;
 
-      const handleEvent = (manager, event) => {
+      const handleEvent = (
+        manager: PushNotificationManagerType,
+        event: PushNotificationReceivedEventArgs,
+      ) => {
         const byteArray = [];
         for (let i = 0; i < event.payload.length; i++) {
           byteArray.push(event.payload[i]);
@@ -62,7 +69,7 @@
     }
   } else if (process.platform === 'win32' && windowsPushNotificationManager) {
     try {
-      const token = await new Promise((resolvePromise, reject) => {
+      const token = await new Promise<string>((resolvePromise, reject) => {
         windowsPushNotificationManager.createChannelAsync(
           'f09f4211-a998-40c1-a515-689e3faecb62',
           (error, result) => {