diff --git a/apps/api/src/app/account/account.service.ts b/apps/api/src/app/account/account.service.ts
index 4663e387b..3d0bb91bd 100644
--- a/apps/api/src/app/account/account.service.ts
+++ b/apps/api/src/app/account/account.service.ts
@@ -25,7 +25,7 @@ import {
 } from '@prisma/client';
 import { Big } from 'big.js';
 import { endOfToday, format } from 'date-fns';
-import { groupBy } from 'lodash';
+import { groupBy, isNil } from 'lodash';
 
 import { CashDetails } from './interfaces/cash-details.interface';
 
@@ -189,7 +189,7 @@ export class AccountService {
       }
     });
 
-    if (balance !== undefined) {
+    if (!isNil(balance)) {
       await this.accountBalanceService.createOrUpdateAccountBalance({
         balance,
         userId,
@@ -311,7 +311,7 @@ export class AccountService {
     userId,
     where
   }: {
-    balance: number;
+    balance?: number;
     data: Prisma.AccountUpdateInput;
     tagIds?: string[];
     userId: string;
@@ -336,12 +336,14 @@ export class AccountService {
       where
     });
 
-    await this.accountBalanceService.createOrUpdateAccountBalance({
-      balance,
-      userId,
-      accountId: account.id,
-      date: format(new Date(), DATE_FORMAT)
-    });
+    if (!isNil(balance)) {
+      await this.accountBalanceService.createOrUpdateAccountBalance({
+        balance,
+        userId,
+        accountId: account.id,
+        date: format(new Date(), DATE_FORMAT)
+      });
+    }
 
     this.eventEmitter.emit(
       PortfolioChangedEvent.getName(),
diff --git a/libs/common/src/lib/dtos/create-account.dto.ts b/libs/common/src/lib/dtos/create-account.dto.ts
index d9e54e305..ccadff5f9 100644
--- a/libs/common/src/lib/dtos/create-account.dto.ts
+++ b/libs/common/src/lib/dtos/create-account.dto.ts
@@ -14,7 +14,7 @@ import { isString } from 'lodash';
 export class CreateAccountDto {
   /**
    * The initial balance, stored as the account balance of today.
-   * Optional because the balance is derived from the account balances.
+   * Optional because callers may instead supply the full history via `balances`.
    */
   @IsNumber()
   @IsOptional()
diff --git a/libs/common/src/lib/dtos/update-account.dto.ts b/libs/common/src/lib/dtos/update-account.dto.ts
index d8bfc7b8d..4e1570aad 100644
--- a/libs/common/src/lib/dtos/update-account.dto.ts
+++ b/libs/common/src/lib/dtos/update-account.dto.ts
@@ -12,8 +12,13 @@ import {
 import { isString } from 'lodash';
 
 export class UpdateAccountDto {
+  /**
+   * The balance, stored as the account balance of today.
+   * Optional because the account balances are the source of truth.
+   */
   @IsNumber()
-  balance: number;
+  @IsOptional()
+  balance?: number;
 
   @IsOptional()
   @IsString()