diff --git a/backend/app/repositories/customer_repository.py b/backend/app/repositories/customer_repository.py
index 0471601..b1d8688 100644
--- a/backend/app/repositories/customer_repository.py
+++ b/backend/app/repositories/customer_repository.py
@@ -23,6 +23,19 @@ def get_by_id(session: Session, customer_id: int) -> Customer | None:
     return session.get(Customer, customer_id)
 
 
+def count_business_refs(session: Session, customer_id: int) -> int:
+    """被业务单据引用的次数（删除保护；业务表就位后补齐的检查）。"""
+    from app.models import Business
+
+    return int(
+        session.execute(
+            select(func.count())
+            .select_from(Business)
+            .where(Business.customer_id == customer_id)
+        ).scalar_one()
+    )
+
+
 def get_with_owner_name(session: Session, customer_id: int) -> Row | None:
     """查单个客户并带出归属人员姓名（详情、编辑回显与归属变更共用）。"""
     stmt = _base_select().where(Customer.id == customer_id)
diff --git a/backend/app/repositories/personnel_repository.py b/backend/app/repositories/personnel_repository.py
index 602e127..3f25451 100644
--- a/backend/app/repositories/personnel_repository.py
+++ b/backend/app/repositories/personnel_repository.py
@@ -94,6 +94,33 @@ def count_customer_ownerships(session: Session, personnel_ids: list[int]) -> dic
     return {int(owner_id): int(count) for owner_id, count in session.execute(stmt).all()}
 
 
+def count_business_roles_refs(session: Session, personnel_ids: list[int]) -> dict[int, int]:
+    """按人员批量统计业务单据归属引用（负责/协助合计；业务表就位后补齐的检查）。
+
+    businesses.owner/assistant_personnel_id 均为 RESTRICT 外键——漏检会让
+    「删除被业务引用的人员」以 500 暴露而非可读的 400。
+    """
+
+    from app.models import Business
+
+    owner = (
+        select(Business.owner_personnel_id, func.count(Business.id))
+        .where(Business.owner_personnel_id.in_(personnel_ids))
+        .group_by(Business.owner_personnel_id)
+    )
+    assistant = (
+        select(Business.assistant_personnel_id, func.count(Business.id))
+        .where(Business.assistant_personnel_id.in_(personnel_ids))
+        .group_by(Business.assistant_personnel_id)
+    )
+    refs: dict[int, int] = {}
+    for stmt in (owner, assistant):
+        for owner_id, count in session.execute(stmt).all():
+            if owner_id is not None:
+                refs[int(owner_id)] = refs.get(int(owner_id), 0) + int(count)
+    return refs
+
+
 def list_regions(session: Session, personnel_id: int) -> list[PersonnelRegion]:
     """查人员的全部辐射区域，按插入顺序返回。"""
     stmt = (
diff --git a/backend/app/schemas/business.py b/backend/app/schemas/business.py
index cfdf5b8..eabd6b0 100644
--- a/backend/app/schemas/business.py
+++ b/backend/app/schemas/business.py
@@ -24,11 +24,18 @@ PRICE_MAX = Decimal("9999999999.9999")
 
 
 def _check_amount(
-    value: str | None, label: str, cap: Decimal, allow_positive_only: bool = False
+    value: str | None,
+    label: str,
+    cap: Decimal,
+    allow_positive_only: bool = False,
+    scale: int = 2,
 ) -> str | None:
-    """字符串金额的通用校验：数字/有限/非负/容量/两位小数。
+    """字符串金额的通用校验：数字/有限/非负/容量/小数位上限。
 
-    小数位超过两位直接拒绝而非静默舍入 —— 舍入即算错钱（工资系统红线）。
+    小数位超限直接拒绝而非静默舍入 —— 舍入即算错钱（工资系统红线）。
+    ``scale`` 按列口径区分：金额/数量列 DECIMAL(14,2) 为 2；单价类列
+    DECIMAL(14,4) 为 4（回显 "5000.0000" 必须能原样提交，否则任何带
+    精度的历史单价都被编辑端点永远拒收）。
     """
     if value is None:
         return None
@@ -45,8 +52,8 @@ def _check_amount(
         raise ValueError(f"{label}不能为负数")
     if amount > cap:
         raise ValueError(f"{label}超出可录入上限")
-    if -amount.as_tuple().exponent > 2:
-        raise ValueError(f"{label}最多两位小数")
+    if -amount.as_tuple().exponent > scale:
+        raise ValueError(f"{label}最多{'两' if scale == 2 else '四'}位小数")
     return value
 
 
@@ -88,10 +95,16 @@ class BusinessItemIn(BaseModel):
     def _check_quantity(cls, value: str) -> str:
         return _check_amount(value, "数量", AMOUNT_MAX, allow_positive_only=True) or value
 
-    @field_validator("sale_price", "cost_amount", "guided_price")
+    @field_validator("sale_price", "guided_price")
     @classmethod
-    def _check_prices(cls, value: str | None) -> str | None:
-        return _check_amount(value, "金额", PRICE_MAX)
+    def _check_unit_prices(cls, value: str | None) -> str | None:
+        """单价类字段按 DECIMAL(14,4) 口径校验（4 位小数）。"""
+        return _check_amount(value, "单价", PRICE_MAX, scale=4)
+
+    @field_validator("cost_amount")
+    @classmethod
+    def _check_cost(cls, value: str | None) -> str | None:
+        return _check_amount(value, "金额", AMOUNT_MAX)
 
 
 class BusinessItemOut(BaseModel):
diff --git a/backend/app/schemas/shipment.py b/backend/app/schemas/shipment.py
index 9ce2377..2df61d9 100644
--- a/backend/app/schemas/shipment.py
+++ b/backend/app/schemas/shipment.py
@@ -40,7 +40,8 @@ class ShipmentItemIn(BaseModel):
     @field_validator("sale_price")
     @classmethod
     def _check_price(cls, value: str | None) -> str | None:
-        return _check_amount(value, "金额", PRICE_MAX)
+        """发货单价列 DECIMAL(14,4)：按 4 位小数口径（回显可原样提交）。"""
+        return _check_amount(value, "单价", PRICE_MAX, scale=4)
 
 
 class ShipmentItemOut(BaseModel):
diff --git a/backend/app/services/customer_service.py b/backend/app/services/customer_service.py
index c4da6e7..1329c7d 100644
--- a/backend/app/services/customer_service.py
+++ b/backend/app/services/customer_service.py
@@ -294,14 +294,14 @@ def delete_customer(
     operator: User,
     meta: RequestMeta | None = None,
 ) -> None:
-    """删除客户（物理删除）。
+    """删除客户（物理删除）：被业务引用 → 400 引导处理业务单据。
 
-    **被业务数据引用的保护检查待业务数据表（V5）就位后补充**：customers
-    当前仅被 ownership_change_logs 以无外键的固化 ID 引用，而留痕本就要求
-    「被引用方删除后记录仍完整可读」（见 models/customer.py 的固化论证），
-    故现在删除不会产生悬挂外键。
+    businesses.customer_id 为 RESTRICT 外键，引用检查必须先于删除——
+    否则并发窗口内的 FK 冲突会以 500 暴露（T4 时该检查占位、业务表就位
+    后由本处补齐，留痕表是无外键固化不参与拦截）。
 
     :raises NotFoundError: 客户不存在
+    :raises BadRequestError: 客户已被业务单据引用
     """
     customer = customer_repository.get_by_id(session, customer_id)
     with audit_service.audit(
@@ -316,10 +316,17 @@ def delete_customer(
     ):
         if customer is None:
             raise NotFoundError("客户不存在")
+        if customer_repository.count_business_refs(session, customer_id):
+            raise BadRequestError("该客户已存在关联业务，请先处理相关业务单据")
 
         company_name = customer.company_name  # 固化：对象随删除失效
-        customer_repository.delete(session, customer)
-        session.commit()
+        try:
+            customer_repository.delete(session, customer)
+            session.commit()
+        except IntegrityError as exc:
+            # 先查后删的并发窗口：新业务挂上了该客户，FK RESTRICT 兜底为 400
+            session.rollback()
+            raise BadRequestError("该客户已存在关联业务，请先处理相关业务单据") from exc
         logger.info("删除客户 | customer_id=%s | company=%s", customer_id, company_name)
 
 
diff --git a/backend/app/services/personnel_service.py b/backend/app/services/personnel_service.py
index 2a06778..606fa3c 100644
--- a/backend/app/services/personnel_service.py
+++ b/backend/app/services/personnel_service.py
@@ -46,8 +46,9 @@ from app.services.audit_service import AuditRecord, RequestMeta
 
 logger = logging.getLogger(__name__)
 
-# 删除保护的统一文案：两种引用共享同一提示，引导管理员走「离职」而非删除
-_DELETE_BLOCKED = "存在团队成员或客户归属引用，请改为离职而非删除"
+# 删除保护的统一文案：三种引用（团队成员/客户归属/业务归属）共享同一提示，
+# 引导管理员走「离职」而非删除
+_DELETE_BLOCKED = "存在团队成员、客户归属或业务归属引用，请改为离职而非删除"
 
 
 def list_personnel(session: Session, query: PersonnelQuery) -> PageResult[PersonnelOut]:
@@ -229,9 +230,13 @@ def delete_personnel(
             raise NotFoundError("人员不存在")
 
         ids = [personnel_id]
-        if personnel_repository.count_team_members(
-            session, ids
-        ) or personnel_repository.count_customer_ownerships(session, ids):
+        if (
+            personnel_repository.count_team_members(session, ids)
+            or personnel_repository.count_customer_ownerships(session, ids)
+            or personnel_repository.count_business_roles_refs(session, ids)
+        ):
+            # 业务归属引用（负责/协助）随业务表就位一并纳入删除保护——
+            # 漏检会让删除以 FK RESTRICT 的 500 暴露而非可读的 400
             raise BadRequestError(_DELETE_BLOCKED)
 
         name = personnel.personnel_name  # 固化：对象随删除失效
diff --git a/backend/tests/integration/test_customers.py b/backend/tests/integration/test_customers.py
index f290f9f..429fe25 100644
--- a/backend/tests/integration/test_customers.py
+++ b/backend/tests/integration/test_customers.py
@@ -22,6 +22,7 @@ from app.core.constants import (
     CUSTOMER_TYPE_ENTERPRISE,
     CUSTOMER_TYPE_PERSONAL,
     MODULE_CUSTOMER,
+    PRODUCT_CATEGORY_MUNICIPAL_WATER,
 )
 from app.core.db import get_session_factory
 from app.models import BusinessRole, OperationLog, OwnershipChangeLog
@@ -31,6 +32,7 @@ pytestmark = pytest.mark.integration
 
 _PERSONNEL = "/api/v1/base/personnel"
 _CUSTOMERS = "/api/v1/base/customers"
+_BUSINESSES = "/api/v1/business/businesses"
 
 
 def _company() -> str:
@@ -149,6 +151,32 @@ class TestCrudFlow:
         assert dup.status_code == 400, dup.text
         assert "该公司名称与负责人的客户已存在" in dup.json()["message"]
 
+    def test_删除被业务引用的客户_400引导处理单据(
+        self, client: TestClient, normal: dict
+    ) -> None:
+        """业务表就位后删除保护补齐：FK RESTRICT 不能以 500 暴露。"""
+        headers = normal["headers"]
+        customer = _create_customer(client, headers)
+        resp = client.post(
+            _BUSINESSES,
+            json={
+                "customer_id": customer["id"],
+                "items": [
+                    {
+                        "product_name": "t_被引用产品",
+                        "product_category": PRODUCT_CATEGORY_MUNICIPAL_WATER,
+                        "quantity": "1",
+                        "sale_price": "1",
+                    }
+                ],
+            },
+            headers=headers,
+        )
+        assert resp.status_code == 200, resp.text
+        blocked = client.delete(f"{_CUSTOMERS}/{customer['id']}", headers=headers)
+        assert blocked.status_code == 400, blocked.text
+        assert "已存在关联业务" in blocked.json()["message"]
+
     def test_客户分类非法_400(self, client: TestClient, normal: dict) -> None:
         resp = client.post(
             _CUSTOMERS,
diff --git a/backend/tests/integration/test_personnel.py b/backend/tests/integration/test_personnel.py
index 7e2d4a2..a13a5fd 100644
--- a/backend/tests/integration/test_personnel.py
+++ b/backend/tests/integration/test_personnel.py
@@ -29,6 +29,7 @@ pytestmark = pytest.mark.integration
 
 _PERSONNEL = "/api/v1/base/personnel"
 _CUSTOMERS = "/api/v1/base/customers"
+_BUSINESSES = "/api/v1/business/businesses"
 
 
 def _uname() -> str:
@@ -234,7 +235,7 @@ class TestDeleteProtection:
         member = _create(client, headers, manager_id=manager["id"])  # 团队成员占用
         blocked = client.delete(f"{_PERSONNEL}/{manager['id']}", headers=headers)
         assert blocked.status_code == 400, blocked.text
-        assert "存在团队成员或客户归属引用，请改为离职而非删除" in blocked.json()["message"]
+        assert "存在团队成员、客户归属或业务归属引用，请改为离职而非删除" in blocked.json()["message"]
 
         client.delete(f"{_PERSONNEL}/{member['id']}", headers=headers)
         freed = client.delete(f"{_PERSONNEL}/{manager['id']}", headers=headers)
@@ -260,7 +261,7 @@ class TestDeleteProtection:
 
         blocked = client.delete(f"{_PERSONNEL}/{owner['id']}", headers=headers)
         assert blocked.status_code == 400, blocked.text
-        assert "存在团队成员或客户归属引用，请改为离职而非删除" in blocked.json()["message"]
+        assert "存在团队成员、客户归属或业务归属引用，请改为离职而非删除" in blocked.json()["message"]
 
         # 保护与在职状态无关：离职并不能让物理删除放行
         client.put(f"{_PERSONNEL}/{owner['id']}/status", json={"status": 0}, headers=headers)
@@ -269,6 +270,55 @@ class TestDeleteProtection:
 
         # 删客户解除引用后方可删人
         assert client.delete(f"{_CUSTOMERS}/{customer['id']}", headers=headers).status_code == 200
+        freed = client.delete(f"{_PERSONNEL}/{owner['id']}", headers=headers)
+        assert freed.status_code == 200, freed.text
+
+    def test_被业务归属引用禁删_负责或协助任一即拦(
+        self, client: TestClient, normal: dict
+    ) -> None:
+        """业务表就位后删除保护补齐：负责/协助引用任一即拦，FK 不以 500 暴露。"""
+        headers = normal["headers"]
+        owner = _create(client, headers)
+        assistant = _create(client, headers)
+        resp_customer = client.post(
+            _CUSTOMERS,
+            json={
+                "company_name": f"t_公司_{uuid.uuid4().hex[:8]}",
+                "owner_name": "张老板",
+                "customer_type": "personal",
+            },
+            headers=headers,
+        )
+        assert resp_customer.status_code == 200, resp_customer.text
+        customer_id = resp_customer.json()["data"]["id"]
+        resp = client.post(
+            _BUSINESSES,
+            json={
+                "customer_id": customer_id,
+                "owner_personnel_id": owner["id"],
+                "assistant_personnel_id": assistant["id"],
+                "items": [
+                    {
+                        "product_name": "t_引用产品",
+                        "product_category": "municipal_water",
+                        "quantity": "1",
+                        "sale_price": "1",
+                    }
+                ],
+            },
+            headers=headers,
+        )
+        assert resp.status_code == 200, resp.text
+
+        for target, label in ((owner, "负责"), (assistant, "协助")):
+            blocked = client.delete(f"{_PERSONNEL}/{target['id']}", headers=headers)
+            assert blocked.status_code == 400, blocked.text
+            assert "业务归属" in blocked.json()["message"], f"{label}引用未拦截"
+
+        # 删除业务解除引用后，人员方可删除（owner 仍被客户归属引用，先删客户）
+        business_id = resp.json()["data"]["id"]
+        assert client.delete(f"{_BUSINESSES}/{business_id}", headers=headers).status_code == 200
+        assert client.delete(f"{_CUSTOMERS}/{customer_id}", headers=headers).status_code == 200
         assert client.delete(f"{_PERSONNEL}/{owner['id']}", headers=headers).status_code == 200