diff --git a/src/app/(protected)/workorders/_components/list/table/wo-table-row-service-cells.tsx b/src/app/(protected)/workorders/_components/list/table/wo-table-row-service-cells.tsx
index ad995968..21731f67 100644
--- a/src/app/(protected)/workorders/_components/list/table/wo-table-row-service-cells.tsx
+++ b/src/app/(protected)/workorders/_components/list/table/wo-table-row-service-cells.tsx
@@ -114,6 +114,9 @@ export function WoTableRowServiceCells({
           value={row.completedDate}
           q={search}
           onSave={(date) => onPatchRow({ completedDate: date })}
+          onClear={
+            row.completedDate && !viewOnly ? () => onPatchRow({ completedDate: "" }) : undefined
+          }
         />
       </td>
       <td style={{ padding: "0 14px" }} onClick={(e) => e.stopPropagation()}>
diff --git a/src/test/app/(protected)/workorders/wo-table-completed-date-clear.test.tsx b/src/test/app/(protected)/workorders/wo-table-completed-date-clear.test.tsx
new file mode 100644
index 00000000..6e2c5ccd
--- /dev/null
+++ b/src/test/app/(protected)/workorders/wo-table-completed-date-clear.test.tsx
@@ -0,0 +1,128 @@
+import { fireEvent, screen } from "@testing-library/react";
+import { describe, expect, it, vi } from "vitest";
+import { WoTableRowServiceCells } from "@/app/(protected)/workorders/_components/list/table/wo-table-row-service-cells";
+import type { WoTableRowHandlers } from "@/app/(protected)/workorders/_components/list/table/wo-table-row";
+import type { WorkOrderTableRow } from "@/domain/work-orders/types/work-order-table-row";
+import { renderWithProviders } from "@/test/test-utils";
+
+function makeRow(overrides: Partial<WorkOrderTableRow> = {}): WorkOrderTableRow {
+  return {
+    id: 9,
+    woNumber: "24818000001",
+    site: "BK5",
+    type: "PM",
+    severity: null,
+    dispatcherId: "u1",
+    dispatcherName: "Alex",
+    scheduledOn: "2026-07-15",
+    completedDate: "2026-07-20",
+    targetWeek: "2026-07-15",
+    dayGroup: "07/15",
+    dayLabel: "Tue",
+    location: "Lobby",
+    locationId: "loc-1",
+    pm: "HVAC",
+    serviceNotes: "",
+    extraServices: [],
+    vendorId: "7",
+    company: "Acme",
+    tech: "Sam",
+    techPhone: "",
+    apptStart: "",
+    apptEnd: "",
+    apptTime: "09:00 – 10:00",
+    status: "Incomplete",
+    docStatus: "Yes",
+    pocName: "",
+    pocPhone: "",
+    pocNotes: "",
+    dueDate: "2026-07-22",
+    rescheduleCount: 0,
+    carriedOver: 0,
+    originalWeek: "",
+    originalDate: "",
+    isPastDue: false,
+    scheduleWeekOnly: false,
+    isAddOn: false,
+    mediaCount: 1,
+    title: "",
+    priority: "",
+    primaryDispatchId: null,
+    rowVersion: "",
+    dispatchRowVersion: "",
+    flagColor: null,
+    additionalContacts: [],
+    upliftSummary: { hasUplift: false, pendingCount: 0 },
+    ...overrides,
+  };
+}
+
+const handlers: WoTableRowHandlers = {
+  onRowClick: vi.fn(),
+  onView: vi.fn(),
+  onEdit: vi.fn(),
+  onOpenMedia: vi.fn(),
+  onPatch: vi.fn(),
+  onScheduleDate: vi.fn(),
+  onScheduleWeek: vi.fn(),
+  onScheduleRange: vi.fn(),
+  onOpenSlideOver: vi.fn(),
+  onOpenCompDoc: vi.fn(),
+  onOpenUplifts: vi.fn(),
+  onReorder: vi.fn(),
+  onDragStart: vi.fn(),
+  onDragOver: vi.fn(),
+  onDrop: vi.fn(),
+  onDragEnd: vi.fn(),
+};
+
+function renderCells(row: WorkOrderTableRow, viewOnly = false) {
+  const onPatchRow = vi.fn();
+  renderWithProviders(
+    <table>
+      <tbody>
+        <tr>
+          <WoTableRowServiceCells
+            row={row}
+            vendors={[]}
+            pmTypes={[]}
+            viewOnly={viewOnly}
+            handlers={handlers}
+            onPatchRow={onPatchRow}
+          />
+        </tr>
+      </tbody>
+    </table>,
+  );
+  return onPatchRow;
+}
+
+describe("WoTableRowServiceCells completed date Clear (SH-390)", () => {
+  it("shows Clear in the completed-date editor and patches completedDate to empty", async () => {
+    const onPatchRow = renderCells(makeRow());
+
+    fireEvent.click(screen.getByRole("button", { name: /07-20/ }));
+
+    fireEvent.click(await screen.findByRole("button", { name: /clear/i }));
+
+    expect(onPatchRow).toHaveBeenCalledWith({ completedDate: "" });
+  });
+
+  it("offers no Clear when the completed date is already empty", async () => {
+    renderCells(makeRow({ completedDate: "" }));
+
+    fireEvent.click(screen.getByRole("button", { name: "—" }));
+
+    expect(await screen.findByRole("button", { name: "20" })).toBeInTheDocument();
+    expect(screen.queryByRole("button", { name: /clear/i })).not.toBeInTheDocument();
+  });
+
+  it("offers no Clear on a Completed (view-only) row", async () => {
+    renderCells(makeRow({ status: "Completed" }), true);
+
+    fireEvent.click(screen.getByRole("button", { name: /07-20/ }));
+
+    expect(await screen.findByRole("button", { name: "20" })).toBeInTheDocument();
+    expect(screen.queryByRole("button", { name: /clear/i })).not.toBeInTheDocument();
+  });
+});
diff --git a/src/test/app/(protected)/workorders/wo-table-row-completed-date-clear.test.tsx b/src/test/app/(protected)/workorders/wo-table-row-completed-date-clear.test.tsx
new file mode 100644
index 00000000..84275975
--- /dev/null
+++ b/src/test/app/(protected)/workorders/wo-table-row-completed-date-clear.test.tsx
@@ -0,0 +1,128 @@
+import { fireEvent, screen } from "@testing-library/react";
+import { describe, expect, it, vi } from "vitest";
+import { WoTableRow } from "@/app/(protected)/workorders/_components/list/table/wo-table-row";
+import type { WoTableRowHandlers } from "@/app/(protected)/workorders/_components/list/table/wo-table-row";
+import type { WorkOrderTableRow } from "@/domain/work-orders/types/work-order-table-row";
+import { renderWithProviders } from "@/test/test-utils";
+
+function makeRow(overrides: Partial<WorkOrderTableRow> = {}): WorkOrderTableRow {
+  return {
+    id: 9,
+    woNumber: "24818000001",
+    site: "BK5",
+    type: "PM",
+    severity: null,
+    dispatcherId: "u1",
+    dispatcherName: "Alex",
+    scheduledOn: "2026-07-15",
+    completedDate: "2026-07-20",
+    targetWeek: "2026-07-15",
+    dayGroup: "07/15",
+    dayLabel: "Tue",
+    location: "Lobby",
+    locationId: "loc-1",
+    pm: "HVAC",
+    serviceNotes: "",
+    extraServices: [],
+    vendorId: "7",
+    company: "Acme",
+    tech: "Sam",
+    techPhone: "",
+    apptStart: "",
+    apptEnd: "",
+    apptTime: "09:00 – 10:00",
+    status: "Incomplete",
+    docStatus: "Yes",
+    pocName: "",
+    pocPhone: "",
+    pocNotes: "",
+    dueDate: "2026-07-22",
+    rescheduleCount: 0,
+    carriedOver: 0,
+    originalWeek: "",
+    originalDate: "",
+    isPastDue: false,
+    scheduleWeekOnly: false,
+    isAddOn: false,
+    mediaCount: 1,
+    title: "",
+    priority: "",
+    primaryDispatchId: null,
+    rowVersion: "",
+    dispatchRowVersion: "",
+    flagColor: null,
+    additionalContacts: [],
+    upliftSummary: { hasUplift: false, pendingCount: 0 },
+    ...overrides,
+  };
+}
+
+function makeHandlers(): WoTableRowHandlers {
+  return {
+    onRowClick: vi.fn(),
+    onView: vi.fn(),
+    onEdit: vi.fn(),
+    onOpenMedia: vi.fn(),
+    onPatch: vi.fn(),
+    onScheduleDate: vi.fn(),
+    onScheduleWeek: vi.fn(),
+    onScheduleRange: vi.fn(),
+    onOpenSlideOver: vi.fn(),
+    onOpenCompDoc: vi.fn(),
+    onOpenUplifts: vi.fn(),
+    onReorder: vi.fn(),
+    onDragStart: vi.fn(),
+    onDragOver: vi.fn(),
+    onDrop: vi.fn(),
+    onDragEnd: vi.fn(),
+  };
+}
+
+function renderRow(row: WorkOrderTableRow, handlers: WoTableRowHandlers) {
+  renderWithProviders(
+    <table>
+      <tbody>
+        <WoTableRow
+          row={row}
+          allRows={[row]}
+          users={[]}
+          sites={[]}
+          vendors={[]}
+          pmTypes={["HVAC"]}
+          isSelected={false}
+          isFlashing={false}
+          dragViz={{ dragId: null, overId: null }}
+          handlers={handlers}
+        />
+      </tbody>
+    </table>,
+    { withAuth: false },
+  );
+}
+
+describe("WoTableRow completed date Clear (SH-390)", () => {
+  it("clears the completed date of an open row through the board patch", async () => {
+    const handlers = makeHandlers();
+    renderRow(makeRow(), handlers);
+
+    fireEvent.click(screen.getByRole("button", { name: /07-20/ }));
+    fireEvent.click(await screen.findByRole("button", { name: /clear/i }));
+
+    expect(handlers.onPatch).toHaveBeenCalledTimes(1);
+    expect(vi.mocked(handlers.onPatch).mock.calls[0].slice(0, 2)).toEqual([
+      9,
+      { completedDate: "" },
+    ]);
+  });
+
+  it.each(["Completed", "Canceled"] as const)("offers no Clear on a %s row", async (status) => {
+    const handlers = makeHandlers();
+    renderRow(makeRow({ status }), handlers);
+
+    fireEvent.click(screen.getByRole("button", { name: /07-20/ }));
+
+    expect(await screen.findByRole("button", { name: "20" })).toBeInTheDocument();
+    expect(screen.queryByRole("button", { name: /clear/i })).not.toBeInTheDocument();
+    expect(handlers.onPatch).not.toHaveBeenCalled();
+  });
+});
diff --git a/src/test/domain/work-orders/mappers/completed-date-board-column.test.ts b/src/test/domain/work-orders/mappers/completed-date-board-column.test.ts
index 1820df72..d8a3c17d 100644
--- a/src/test/domain/work-orders/mappers/completed-date-board-column.test.ts
+++ b/src/test/domain/work-orders/mappers/completed-date-board-column.test.ts
@@ -16,6 +16,11 @@ describe("COMPLETED DATE board column wiring", () => {
     expect(ops).toEqual([{ field: "completedDate", value: "2026-07-30" }]);
   });
 
+  it("expands a clearing completedDate patch to an empty-string board field op (SH-390)", () => {
+    const ops = expandScalarBoardOps({ completedDate: "" });
+    expect(ops).toEqual([{ field: "completedDate", value: "" }]);
+  });
+
   it("maps completedDate returned by a board GET row", () => {
     const row = mapWorkOrderTableRow({
       id: 42,