diff --git a/services/nginx/app/classes/department_wash_count_service.php b/services/nginx/app/classes/department_wash_count_service.php
new file mode 100644
index 00000000..8bb55a55
--- /dev/null
+++ b/services/nginx/app/classes/department_wash_count_service.php
@@ -0,0 +1,250 @@
+<?php
+
+namespace classes;
+
+use Exception;
+
+class department_wash_count_service
+{
+    /**
+     * @throws Exception
+     */
+    public function countInDateRange(string $date_start, string $date_end, int $department_id): int
+    {
+        $rows = $this->countByHourForDepartments($date_start, $date_end, [$department_id]);
+        $total = 0;
+
+        foreach ($rows as $row) {
+            $total += (int)($row['wash_count'] ?? 0);
+        }
+
+        return $total;
+    }
+
+    /**
+     * @param array<int|string> $department_ids
+     * @return array<int,array{department_id:int,hour_bucket:string,wash_count:int}>
+     * @throws Exception
+     */
+    public function countByHourForDepartments(string $date_start, string $date_end, array $department_ids): array
+    {
+        global $db;
+
+        $this->validateDateRange($date_start, $date_end);
+        $normalized_department_ids = $this->normalizeIds($department_ids);
+        if ($normalized_department_ids === []) {
+            return [];
+        }
+
+        selfserve_schema_bootstrap::ensureTables();
+
+        $department_ids_sql = implode(',', $normalized_department_ids);
+        $escaped_start = $db->escape_string($date_start);
+        $escaped_end = $db->escape_string($date_end);
+        $candidate_sql = $this->candidateUnionSql($department_ids_sql, $escaped_start, $escaped_end);
+
+        $sql = "SELECT deduped.department_id,
+                       DATE_FORMAT(deduped.counted_at, '%Y-%m-%d %H:00:00') AS hour_bucket,
+                       COUNT(*) AS wash_count
+                FROM (
+                    SELECT dedupe_key,
+                           department_id,
+                           MIN(counted_at) AS counted_at
+                    FROM ($candidate_sql) candidates
+                    GROUP BY dedupe_key, department_id
+                ) deduped
+                GROUP BY deduped.department_id, DATE_FORMAT(deduped.counted_at, '%Y-%m-%d %H:00:00')
+                ORDER BY deduped.department_id ASC, hour_bucket ASC";
+
+        $result = $db->query($sql);
+        if (!is_object($result) || $result->num_rows === 0) {
+            return [];
+        }
+
+        $rows = [];
+        while ($row = $result->fetch_assoc()) {
+            $rows[] = [
+                'department_id' => (int)($row['department_id'] ?? 0),
+                'hour_bucket' => (string)($row['hour_bucket'] ?? ''),
+                'wash_count' => (int)($row['wash_count'] ?? 0),
+            ];
+        }
+
+        return $rows;
+    }
+
+    /**
+     * @param array<int|string> $department_ids
+     * @return array{quantity:int,products:int,earnings:int,washes:int}
+     * @throws Exception
+     */
+    public function transactionSummary(string $date_start, string $date_end, array $department_ids): array
+    {
+        global $db;
+
+        $this->validateDateRange($date_start, $date_end);
+        $normalized_department_ids = $this->normalizeIds($department_ids);
+        if ($normalized_department_ids === []) {
+            return [
+                'quantity' => 0,
+                'products' => 0,
+                'earnings' => 0,
+                'washes' => 0,
+            ];
+        }
+
+        $department_ids_sql = implode(',', $normalized_department_ids);
+        $escaped_start = $db->escape_string($date_start);
+        $escaped_end = $db->escape_string($date_end);
+
+        $sql = "SELECT COUNT(DISTINCT o.id) AS quantity,
+                       COALESCE(SUM(oi.quantity), 0) AS products,
+                       COALESCE(SUM(oi.price * oi.quantity), 0) AS earnings
+                FROM orders o
+                JOIN order_items oi ON oi.order_id = o.id
+                WHERE o.department_id IN ($department_ids_sql)
+                  AND o.created_at BETWEEN '$escaped_start' AND '$escaped_end'
+                  AND o.deleted_at IS NULL
+                  AND oi.deleted_at IS NULL";
+
+        $result = $db->query($sql);
+        $row = is_object($result) ? $result->fetch_assoc() : null;
+
+        return [
+            'quantity' => (int)($row['quantity'] ?? 0),
+            'products' => (int)($row['products'] ?? 0),
+            'earnings' => (int)round((float)($row['earnings'] ?? 0)),
+            'washes' => $this->countRows($date_start, $date_end, $normalized_department_ids),
+        ];
+    }
+
+    /**
+     * @param array<int|string> $department_ids
+     * @return array<int,array{id:int,department_id:int,created_at:string}>
+     * @throws Exception
+     */
+    public function listTransactions(string $date_start, string $date_end, array $department_ids): array
+    {
+        global $db;
+
+        $this->validateDateRange($date_start, $date_end);
+        $normalized_department_ids = $this->normalizeIds($department_ids);
+        if ($normalized_department_ids === []) {
+            return [];
+        }
+
+        selfserve_schema_bootstrap::ensureTables();
+
+        $department_ids_sql = implode(',', $normalized_department_ids);
+        $escaped_start = $db->escape_string($date_start);
+        $escaped_end = $db->escape_string($date_end);
+        $candidate_sql = $this->candidateUnionSql($department_ids_sql, $escaped_start, $escaped_end);
+
+        $sql = "SELECT CAST(SUBSTRING_INDEX(GROUP_CONCAT(entity_id ORDER BY source_priority ASC, entity_id ASC), ',', 1) AS UNSIGNED) AS id,
+                       department_id,
+                       MIN(counted_at) AS created_at
+                FROM ($candidate_sql) candidates
+                GROUP BY dedupe_key, department_id
+                ORDER BY created_at ASC";
+
+        $result = $db->query($sql);
+        if (!is_object($result) || $result->num_rows === 0) {
+            return [];
+        }
+
+        $rows = [];
+        while ($row = $result->fetch_assoc()) {
+            $rows[] = [
+                'id' => (int)($row['id'] ?? 0),
+                'department_id' => (int)($row['department_id'] ?? 0),
+                'created_at' => (string)($row['created_at'] ?? ''),
+            ];
+        }
+
+        return $rows;
+    }
+
+    /**
+     * @param array<int> $department_ids
+     * @throws Exception
+     */
+    private function countRows(string $date_start, string $date_end, array $department_ids): int
+    {
+        $rows = $this->countByHourForDepartments($date_start, $date_end, $department_ids);
+        $total = 0;
+
+        foreach ($rows as $row) {
+            $total += (int)($row['wash_count'] ?? 0);
+        }
+
+        return $total;
+    }
+
+    private function candidateUnionSql(string $department_ids_sql, string $escaped_start, string $escaped_end): string
+    {
+        return "SELECT CONCAT('order:', o.id) AS dedupe_key,
+                       o.id AS entity_id,
+                       o.department_id,
+                       o.created_at AS counted_at,
+                       0 AS source_priority
+                FROM orders o
+                JOIN order_items oi ON oi.order_id = o.id
+                JOIN products p ON p.id = oi.product_id
+                WHERE o.department_id IN ($department_ids_sql)
+                  AND o.created_at BETWEEN '$escaped_start' AND '$escaped_end'
+                  AND o.deleted_at IS NULL
+                  AND oi.deleted_at IS NULL
+                  AND p.is_wash = 1
+                UNION ALL
+                SELECT CASE
+                           WHEN linked_o.id IS NOT NULL THEN CONCAT('order:', linked_o.id)
+                           ELSE CONCAT('selfserve:', s.id)
+                       END AS dedupe_key,
+                       CASE
+                           WHEN linked_o.id IS NOT NULL THEN linked_o.id
+                           ELSE s.id
+                       END AS entity_id,
+                       COALESCE(linked_o.department_id, s.department_id) AS department_id,
+                       COALESCE(linked_o.created_at, s.completed_at) AS counted_at,
+                       1 AS source_priority
+                FROM selfserve_wash_sessions s
+                LEFT JOIN orders linked_o
+                  ON linked_o.id = s.order_id
+                 AND linked_o.deleted_at IS NULL
+                WHERE COALESCE(linked_o.department_id, s.department_id) IN ($department_ids_sql)
+                  AND COALESCE(linked_o.created_at, s.completed_at) BETWEEN '$escaped_start' AND '$escaped_end'
+                  AND s.deleted_at IS NULL
+                  AND s.completed_at IS NOT NULL
+                  AND UPPER(TRIM(s.status)) = 'COMPLETED'";
+    }
+
+    /**
+     * @param array<int|string> $ids
+     * @return array<int>
+     */
+    private function normalizeIds(array $ids): array
+    {
+        $normalized = [];
+        foreach ($ids as $id) {
+            $value = (int)$id;
+            if ($value > 0) {
+                $normalized[$value] = $value;
+            }
+        }
+
+        return array_values($normalized);
+    }
+
+    /**
+     * @throws Exception
+     */
+    private function validateDateRange(string $date_start, string $date_end): void
+    {
+        if (strtotime($date_start) === false || strtotime($date_end) === false) {
+            throw new Exception('Invalid date range provided');
+        }
+        if (strtotime($date_start) > strtotime($date_end)) {
+            throw new Exception('The start date cannot be after the end date');
+        }
+    }
+}