diff --git a/apps/backend/src/services/finance/order-refund-service.ts b/apps/backend/src/services/finance/order-refund-service.ts
index 27dca865..25faeb92 100644
--- a/apps/backend/src/services/finance/order-refund-service.ts
+++ b/apps/backend/src/services/finance/order-refund-service.ts
@@ -144,6 +144,7 @@ export async function createManualRefund(
       })
     }
     await assertBasisPeriodOpen(client, order.basis_at, '退款')
+    await assertRefundMonthOpen(client, '退款', toChinaDate(refundedAt || now))
 
     const itemsResult = await client.query<{
       id: number
@@ -396,6 +397,7 @@ export async function voidOrderRefund(
       })
     }
     await assertBasisPeriodOpen(client, row.basis_at, '撤销退款')
+    await assertRefundMonthOpen(client, '撤销退款')
     await client.query(
       `
         UPDATE order_refunds
@@ -490,6 +492,25 @@ export function mapOrderRefund(row: OrderRefundRow): OrderRefund {
   }
 }
 
+async function assertRefundMonthOpen(
+  client: Pick<PoolClient, 'query'>,
+  action: string,
+  date?: string,
+) {
+  const day = date || CHINA_DATE_FORMATTER.format(new Date())
+  const periodKey = day.slice(0, 7)
+  const period = await client.query<{ status: string }>(
+    `SELECT status FROM finance_periods WHERE period_key = $1 LIMIT 1`,
+    [periodKey],
+  )
+  if (period.rows[0]?.status === 'closed') {
+    throw createHttpError(`退款所属期间 ${periodKey} 已关账，请先反关账后再${action}`, {
+      statusCode: 409,
+      errorCode: 'order_refund_period_closed',
+    })
+  }
+}
+
 async function assertBasisPeriodOpen(
   client: Pick<PoolClient, 'query'>,
   basisAt: string,
@@ -664,6 +685,19 @@ export async function approveAndRecordKuaishouRefund(
     }
   }
 
+  // 退款当天所属期间也必须开着，否则退款冲减会静默丢失。
+  const refundPeriodKey = CHINA_DATE_FORMATTER.format(new Date()).slice(0, 7)
+  const refundPeriod = await query<{ status: string }>(
+    `SELECT status FROM finance_periods WHERE period_key = $1 LIMIT 1`,
+    [refundPeriodKey],
+  )
+  if (refundPeriod.rows[0]?.status === 'closed') {
+    throw createHttpError(`退款所属期间 ${refundPeriodKey} 已关账，请先反关账后再退款`, {
+      statusCode: 409,
+      errorCode: 'order_refund_period_closed',
+    })
+  }
+
   // 已经登记过的平台退款必须幂等返回，不能因为剩余可退为 0 被误判为超额。
   const recorded = await findRecordedPlatformRefund(orderId, platformRefundId)
   if (recorded) {