diff --git a/functions/src/index.ts b/functions/src/index.ts
index cf75802e..b3f65a4f 100644
--- a/functions/src/index.ts
+++ b/functions/src/index.ts
@@ -21,6 +21,7 @@ export * from './on-create-group'
 export * from './on-update-user'
 export * from './on-create-comment-on-group'
 export * from './on-create-txn'
+export * from './on-group-delete'
 
 // v2
 export * from './health'
diff --git a/functions/src/on-group-delete.ts b/functions/src/on-group-delete.ts
new file mode 100644
index 00000000..e078bbcd
--- /dev/null
+++ b/functions/src/on-group-delete.ts
@@ -0,0 +1,31 @@
+import * as functions from 'firebase-functions'
+import * as admin from 'firebase-admin'
+
+import { Group } from 'common/group'
+import { Contract } from 'common/contract'
+const firestore = admin.firestore()
+
+exports.onGroupDelete = functions.firestore
+  .document('groups/{groupId}')
+  .onDelete(async (change) => {
+    const group = change.data() as Group
+
+    // get all contracts with this group's slug
+    const contracts = await firestore
+      .collection('contracts')
+      .where('groupSlugs', 'array-contains', group.slug)
+      .get()
+
+    for (const doc of contracts.docs) {
+      const contract = doc.data() as Contract
+      // remove the group from the contract
+      await firestore
+        .collection('contracts')
+        .doc(contract.id)
+        .update({
+          groupSlugs: (contract.groupSlugs ?? []).filter(
+            (groupSlug) => groupSlug !== group.slug
+          ),
+        })
+    }
+  })
diff --git a/web/hooks/use-group.ts b/web/hooks/use-group.ts
index 8af2183e..be0c92f6 100644
--- a/web/hooks/use-group.ts
+++ b/web/hooks/use-group.ts
@@ -2,14 +2,12 @@ import { useEffect, useState } from 'react'
 import { Group } from 'common/group'
 import { User } from 'common/user'
 import {
-  getGroupBySlug,
   getGroupsWithContractId,
   listenForGroup,
   listenForGroups,
   listenForMemberGroups,
 } from 'web/lib/firebase/groups'
 import { getUser } from 'web/lib/firebase/users'
-import { CATEGORIES, CATEGORIES_GROUP_SLUG_POSTFIX } from 'common/categories'
 import { filterDefined } from 'common/util/array'
 
 export const useGroup = (groupId: string | undefined) => {
diff --git a/web/lib/firebase/groups.ts b/web/lib/firebase/groups.ts
index 708096b3..ec152792 100644
--- a/web/lib/firebase/groups.ts
+++ b/web/lib/firebase/groups.ts
@@ -119,6 +119,7 @@ export async function addUserToGroup(
   await updateGroup(newGroup, { memberIds: uniq(newMemberIds) })
   return newGroup
 }
+
 export async function leaveGroup(group: Group, userId: string): Promise<Group> {
   const { memberIds } = group
   if (!memberIds.includes(userId)) {