diff --git a/packages/loot-core/src/mocks/budget.ts b/packages/loot-core/src/mocks/budget.ts
index 7f53c8ac3f9..5d4849e49b6 100644
--- a/packages/loot-core/src/mocks/budget.ts
+++ b/packages/loot-core/src/mocks/budget.ts
@@ -10,6 +10,7 @@ import { batchMessages, setSyncingMode } from '../server/sync';
 import * as monthUtils from '../shared/months';
 import q from '../shared/query';
 import type {
+  CategoryEntity,
   CategoryGroupEntity,
   PayeeEntity,
   TransactionEntity,
@@ -585,7 +586,7 @@ export async function createTestBudget(handlers) {
     }),
   );
 
-  let payees: PayeeEntity[] = [
+  let payees: Array<PayeeEntity & { bill?: boolean }> = [
     { name: 'Starting Balance' },
     { name: 'Kroger' },
     { name: 'Publix' },
@@ -608,7 +609,9 @@ export async function createTestBudget(handlers) {
     }),
   );
 
-  let categoryGroups: CategoryGroupEntity[] = [
+  let categoryGroups: Array<
+    CategoryGroupEntity & { categories: Omit<CategoryEntity, 'group'>[] }
+  > = [
     {
       name: 'Usual Expenses',
       categories: [
@@ -650,7 +653,6 @@ export async function createTestBudget(handlers) {
         isIncome: group.is_income ? 1 : 0,
       });
 
-      // @ts-expect-error Missing proper type refinement
       for (let category of group.categories) {
         category.id = await handlers['category-create']({
           ...category,
diff --git a/packages/loot-core/src/mocks/index.ts b/packages/loot-core/src/mocks/index.ts
index 1759224ad55..3ee4a61dcc8 100644
--- a/packages/loot-core/src/mocks/index.ts
+++ b/packages/loot-core/src/mocks/index.ts
@@ -53,9 +53,8 @@ export function generateCategoryGroups(definition) {
 }
 
 function _generateTransaction(data): TransactionEntity {
-  const id = data.id || uuidv4();
   return {
-    id: id,
+    id: data.id || uuidv4(),
     amount: data.amount || Math.floor(random() * 10000 - 7000),
     payee: data.payee || 'payed-to',
     notes: 'Notes',
@@ -64,7 +63,6 @@ function _generateTransaction(data): TransactionEntity {
     category: data.category,
     sort_order: data.sort_order != null ? data.sort_order : 1,
     cleared: false,
-    error: null,
   };
 }
 
@@ -76,7 +74,7 @@ export function generateTransaction(data, splitAmount?, showError = false) {
 
   if (splitAmount) {
     const parent = trans;
-    parent.isParent = true;
+    parent.is_parent = true;
 
     result.push(
       {
diff --git a/packages/loot-core/src/types/models/account.d.ts b/packages/loot-core/src/types/models/account.d.ts
index 3bb86d4cb95..6bc9ce4d460 100644
--- a/packages/loot-core/src/types/models/account.d.ts
+++ b/packages/loot-core/src/types/models/account.d.ts
@@ -5,7 +5,6 @@ export type AccountEntity = {
   closed: 0 | 1;
   sort_order: number;
   tombstone: 0 | 1;
-  subtype: string | null; // TODO: remove?
 } & (_SyncFields<true> | _SyncFields<false>);
 
 type _SyncFields<T> = {
diff --git a/packages/loot-core/src/types/models/category-group.d.ts b/packages/loot-core/src/types/models/category-group.d.ts
index 227dba003c3..eca289e442e 100644
--- a/packages/loot-core/src/types/models/category-group.d.ts
+++ b/packages/loot-core/src/types/models/category-group.d.ts
@@ -4,6 +4,4 @@ export interface CategoryGroupEntity {
   is_income?: boolean;
   sort_order?: number;
   tombstone?: boolean;
-  // TODO: remove once properly typed
-  [k: string]: unknown;
 }
diff --git a/packages/loot-core/src/types/models/payee.d.ts b/packages/loot-core/src/types/models/payee.d.ts
index 67f14cd306f..381f840b126 100644
--- a/packages/loot-core/src/types/models/payee.d.ts
+++ b/packages/loot-core/src/types/models/payee.d.ts
@@ -5,6 +5,4 @@ export interface PayeeEntity {
   name: string;
   transfer_acct?: AccountEntity;
   tombstone?: boolean;
-  // TODO: remove once properly typed
-  [k: string]: unknown;
 }
diff --git a/packages/loot-core/src/types/models/rule.d.ts b/packages/loot-core/src/types/models/rule.d.ts
index 263cd78b3c9..a374ed29bcf 100644
--- a/packages/loot-core/src/types/models/rule.d.ts
+++ b/packages/loot-core/src/types/models/rule.d.ts
@@ -3,8 +3,7 @@ import { type ScheduleEntity } from './schedule';
 export interface RuleEntity {
   id: string;
   stage: string;
-  conditions_op?: string;
-  conditionsOp?: string; // TODO: this should not be here.. figure out howto remove it
+  conditionsOp: 'any' | 'and';
   conditions: RuleConditionEntity[];
   actions: RuleActionEntity[];
   tombstone?: boolean;
diff --git a/packages/loot-core/src/types/models/transaction.d.ts b/packages/loot-core/src/types/models/transaction.d.ts
index b5366b8d6ea..73103e40cbf 100644
--- a/packages/loot-core/src/types/models/transaction.d.ts
+++ b/packages/loot-core/src/types/models/transaction.d.ts
@@ -15,7 +15,6 @@ export interface TransactionEntity {
   notes?: string;
   date: string;
   imported_id?: string;
-  error?: unknown;
   imported_payee?: string;
   starting_balance_flag?: boolean;
   transfer_id?: string;
@@ -24,6 +23,4 @@ export interface TransactionEntity {
   tombstone?: boolean;
   schedule?: ScheduleEntity;
   subtransactions?: TransactionEntity[];
-  // TODO: remove once properly typed
-  [k: string]: unknown;
 }
diff --git a/upcoming-release-notes/1680.md b/upcoming-release-notes/1680.md
new file mode 100644
index 00000000000..256921d9aa4
--- /dev/null
+++ b/upcoming-release-notes/1680.md
@@ -0,0 +1,6 @@
+---
+category: Maintenance
+authors: [MatissJanis]
+---
+
+Typescript: hardening data entity types