diff --git a/crates/ledger-cli/tests/spec_mcp.rs b/crates/ledger-cli/tests/spec_mcp.rs
index ede855a..4a3bc23 100644
--- a/crates/ledger-cli/tests/spec_mcp.rs
+++ b/crates/ledger-cli/tests/spec_mcp.rs
@@ -896,6 +896,20 @@ fn happy_path(name: &str) -> Mcp {
         json!({"kind": "invoices", "status": "all"}),
     );
     m.ok("books.document", json!({"ref": format!("invoice:{inv}")}));
+    // P4b S7: a bad debt, its evidence uploaded and filed with it.
+    let bad = m.ok(
+        "books.create_invoice",
+        json!({"party_id": customer, "date": "2026-02-03", "due_date": "2026-03-03",
+               "lines": [{"description": "Consulting, never paid", "amount": "400.00"}]}),
+    )["id"]
+        .as_u64()
+        .unwrap();
+    let letter = m.upload(b"Final demand", "letter.txt", "text/plain", "document");
+    m.ok(
+        "books.write_off_invoice",
+        json!({"invoice": bad, "date": "2026-03-01", "reason": "collection exhausted",
+               "upload_id": letter, "confirmed": true}),
+    );
 
     // Fixed assets.
     let registered = m.ok(