diff --git a/server/src/Models/CashFlow/CashFlow.Adapter.Mongoose.ts b/server/src/Models/CashFlow/CashFlow.Adapter.Mongoose.ts
index 9bce510..cf73881 100644
--- a/server/src/Models/CashFlow/CashFlow.Adapter.Mongoose.ts
+++ b/server/src/Models/CashFlow/CashFlow.Adapter.Mongoose.ts
@@ -99,7 +99,9 @@ export class CashFlowAdapterMongoose implements ICashFlowAdapter {
             searchCriteria.year = filters.year;
         }
 
-        if (filters.month) {
+        // month 0 = enero: no usar truthy check, si no se dropea el filtro y enero
+        // queda sin filtrar (devolvería todos los meses del año).
+        if (typeof filters.month === "number") {
             searchCriteria.month = filters.month;
         }
 
diff --git a/server/src/Models/CashFlowBalance/CashFlowBalance.Adapter.Mongoose.ts b/server/src/Models/CashFlowBalance/CashFlowBalance.Adapter.Mongoose.ts
index 746526a..dc7a035 100644
--- a/server/src/Models/CashFlowBalance/CashFlowBalance.Adapter.Mongoose.ts
+++ b/server/src/Models/CashFlowBalance/CashFlowBalance.Adapter.Mongoose.ts
@@ -45,7 +45,8 @@ export class CashFlowBalanceAdapterMongoose implements ICashFlowBalanceAdapter {
             searchCriteria.companyId = filters.companyId;
         }
 
-        if (filters.month) {
+        // month 0 = enero: no usar truthy check, si no se dropea el filtro.
+        if (typeof filters.month === "number") {
             searchCriteria.month = filters.month;
         }
 
diff --git a/server/src/Models/CashFlowBalance/CashFlowBalance.ts b/server/src/Models/CashFlowBalance/CashFlowBalance.ts
index 6a643fa..47e1cc7 100644
--- a/server/src/Models/CashFlowBalance/CashFlowBalance.ts
+++ b/server/src/Models/CashFlowBalance/CashFlowBalance.ts
@@ -231,7 +231,10 @@ class CashFlowBalanceManager implements ICashFlowBalanceManager {
         const userSession = await this.validateSessionUser(data.sessionUser);
         await this.validatePermissions(String(userSession.id), data.companyId);
 
-        const months = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12];
+        // Los balances se guardan con month 0-indexado (0 = enero ... 11 = diciembre),
+        // igual que dayjs.month(). No iterar de 1 a 12: eso saltea enero (key 0)
+        // y consultaba un mes 12 inexistente que el cliente renderiza como enero del año siguiente.
+        const months = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11];
         const year = data.year;
         const companyId = data.companyId;
 
diff --git a/txclient/src/app/admin/(organization-profile)/org/profile/[id]/cash/resume/page.tsx b/txclient/src/app/admin/(organization-profile)/org/profile/[id]/cash/resume/page.tsx
index a44a27b..9f57f55 100644
--- a/txclient/src/app/admin/(organization-profile)/org/profile/[id]/cash/resume/page.tsx
+++ b/txclient/src/app/admin/(organization-profile)/org/profile/[id]/cash/resume/page.tsx
@@ -149,7 +149,9 @@ export default function OrganizationCashFlowResume() {
         cashFlowCalculateBalance({
             companyId: id,
             year: year,
-            month: month,
+            // TextMonth maneja meses 1-indexados (1 = enero); el storage de balances es
+            // 0-indexado (dayjs.month()), así que convertimos antes de enviar.
+            month: month - 1,
             sessionUser: SessionInfo.userId,
         })
             .then(() => {