diff --git a/backend/src/features/maintenance/data/maintenance.repository.ts b/backend/src/features/maintenance/data/maintenance.repository.ts
index 52c948e..0c862b9 100644
--- a/backend/src/features/maintenance/data/maintenance.repository.ts
+++ b/backend/src/features/maintenance/data/maintenance.repository.ts
@@ -18,7 +18,8 @@ export class MaintenanceRepository {
       subtypes: row.subtypes,
       date: row.date,
       odometerReading: row.odometer_reading,
-      cost: row.cost,
+      // node-postgres returns numeric/decimal columns as strings; coerce to honor the number type.
+      cost: row.cost != null ? Number(row.cost) : undefined,
       shopName: row.shop_name,
       notes: row.notes,
       receiptDocumentId: row.receipt_document_id,
diff --git a/backend/src/features/ownership-costs/data/ownership-costs.repository.ts b/backend/src/features/ownership-costs/data/ownership-costs.repository.ts
index 6096d06..1119eb6 100644
--- a/backend/src/features/ownership-costs/data/ownership-costs.repository.ts
+++ b/backend/src/features/ownership-costs/data/ownership-costs.repository.ts
@@ -16,7 +16,8 @@ export class OwnershipCostsRepository {
       vehicleId: row.vehicle_id,
       documentId: row.document_id,
       costType: row.cost_type,
-      amount: row.amount,
+      // node-postgres returns numeric/decimal columns as strings; coerce to honor the number type.
+      amount: Number(row.amount),
       description: row.description,
       periodStart: row.period_start,
       periodEnd: row.period_end,
diff --git a/frontend/src/features/maintenance/components/MaintenanceRecordsList.tsx b/frontend/src/features/maintenance/components/MaintenanceRecordsList.tsx
index 0bc0180..314105d 100644
--- a/frontend/src/features/maintenance/components/MaintenanceRecordsList.tsx
+++ b/frontend/src/features/maintenance/components/MaintenanceRecordsList.tsx
@@ -115,16 +115,16 @@ export const MaintenanceRecordsList: React.FC<MaintenanceRecordsListProps> = ({
                       {categoryDisplay} ({subtypeCount})
                     </Typography>
                     <Stack direction="row" spacing={1} flexWrap="wrap" sx={{ mt: 1 }}>
-                      {record.odometerReading && (
+                      {record.odometerReading != null && (
                         <Chip
-                          label={`${Number(record.odometerReading).toLocaleString()} miles`}
+                          label={`${record.odometerReading.toLocaleString()} miles`}
                           size="small"
                           variant="outlined"
                         />
                       )}
-                      {record.cost && (
+                      {record.cost != null && (
                         <Chip
-                          label={`$${Number(record.cost).toFixed(2)}`}
+                          label={`$${record.cost.toFixed(2)}`}
                           size="small"
                           color="primary"
                           variant="outlined"
diff --git a/frontend/src/features/vehicles/mobile/VehicleDetailMobile.tsx b/frontend/src/features/vehicles/mobile/VehicleDetailMobile.tsx
index b241054..bef18a7 100644
--- a/frontend/src/features/vehicles/mobile/VehicleDetailMobile.tsx
+++ b/frontend/src/features/vehicles/mobile/VehicleDetailMobile.tsx
@@ -142,9 +142,7 @@ export const VehicleDetailMobile: React.FC<VehicleDetailMobileProps> = ({
         secondaryParts.push(new Date(rec.date).toLocaleDateString());
         secondaryParts.push('Maintenance');
         const secondary = secondaryParts.join(' • ');
-        // Backend returns numeric/decimal columns as strings via node-postgres; coerce.
-        const costNum = rec.cost != null ? Number(rec.cost) : NaN;
-        const amount = Number.isFinite(costNum) ? `$${costNum.toFixed(2)}` : undefined;
+        const amount = typeof rec.cost === 'number' ? `$${rec.cost.toFixed(2)}` : undefined;
         list.push({
           id: rec.id,
           type: 'Maintenance',
diff --git a/frontend/src/features/vehicles/pages/VehicleDetailPage.tsx b/frontend/src/features/vehicles/pages/VehicleDetailPage.tsx
index 4bdce5b..65e7e0f 100644
--- a/frontend/src/features/vehicles/pages/VehicleDetailPage.tsx
+++ b/frontend/src/features/vehicles/pages/VehicleDetailPage.tsx
@@ -148,9 +148,7 @@ export const VehicleDetailPage: React.FC = () => {
         if (subtypeText) parts.push(subtypeText);
         if (rec.shopName) parts.push(rec.shopName);
         const summary = parts.join(' • ');
-        // Backend returns numeric/decimal columns as strings via node-postgres; coerce.
-        const costNum = rec.cost != null ? Number(rec.cost) : NaN;
-        const amount = Number.isFinite(costNum) ? `$${costNum.toFixed(2)}` : undefined;
+        const amount = typeof rec.cost === 'number' ? `$${rec.cost.toFixed(2)}` : undefined;
         list.push({ id: rec.id, type: 'Maintenance', date: rec.date, summary, amount });
       }
     }