diff --git a/backend/testhelpers/tradecycles.sh b/backend/testhelpers/tradecycles.sh
new file mode 100755
index 0000000..f2f5831
--- /dev/null
+++ b/backend/testhelpers/tradecycles.sh
@@ -0,0 +1,56 @@
+curl --location '127.0.0.1:18881/api/v1/trades' \
+--header 'Content-Type: application/json' \
+--header 'Cookie: session_token=uYsEZZdH9ecQ432HQUdfab292I14suk4GuI12-cAyuw' \
+--data '{
+    "friendly_name": "20250908-CA-PUT",
+    "symbol": "CA",
+    "exchange_id": 1,
+    "underlying_currency": "EUR",
+    "trade_type": "SELL_PUT",
+    "trade_strategy": "WHEEL",
+    "trade_date": "2025-09-08",
+    "quantity": 1,
+    "quantity_multiplier": 100,
+    "price_cents": 17,
+    "expiry_date": "2025-09-09",
+    "strike_price_cents": 1220,
+    "commission_cents": 114
+}'
+
+curl --location '127.0.0.1:18881/api/v1/trades' \
+--header 'Content-Type: application/json' \
+--header 'Cookie: session_token=uYsEZZdH9ecQ432HQUdfab292I14suk4GuI12-cAyuw' \
+--data '{
+    "friendly_name": "20250920-CA-ASSIGN",
+    "symbol": "CA",
+    "exchange_id": 1,
+    "cycle_id": 1,
+    "underlying_currency": "EUR",
+    "trade_type": "ASSIGNMENT",
+    "trade_strategy": "WHEEL",
+    "trade_date": "2025-09-20",
+    "quantity": 100,
+    "quantity_multiplier": 1,
+    "price_cents": 1220,
+    "commission_cents": 0
+}'
+
+curl --location '127.0.0.1:18881/api/v1/trades' \
+--header 'Content-Type: application/json' \
+--header 'Cookie: session_token=uYsEZZdH9ecQ432HQUdfab292I14suk4GuI12-cAyuw' \
+--data '{
+    "friendly_name": "20250923-CA-CALL",
+    "symbol": "CA",
+    "exchange_id": 1,
+    "cycle_id": 1,
+    "underlying_currency": "EUR",
+    "trade_type": "SELL_CALL",
+    "trade_strategy": "WHEEL",
+    "trade_date": "2025-09-23",
+    "quantity": 1,
+    "quantity_multiplier": 100,
+    "price_cents": 31,
+    "expiry_date": "2025-10-10",
+    "strike_price_cents": 1200,
+    "commission_cents": 114
+}'
\ No newline at end of file
diff --git a/backend/trading_journal/dto.py b/backend/trading_journal/dto.py
index 1851b0d..0dd227f 100644
--- a/backend/trading_journal/dto.py
+++ b/backend/trading_journal/dto.py
@@ -69,7 +69,7 @@ class CycleBase(SQLModel):
     funding_source: str | None = None
     capital_exposure_cents: int | None = None
     loan_amount_cents: int | None = None
-    loan_interest_rate_bps: int | None = None
+    loan_interest_rate_tenth_bps: int | None = None
     trades: list[TradeRead] | None = None
     exchange: ExchangesRead | None = None
 
diff --git a/backend/trading_journal/service.py b/backend/trading_journal/service.py
index 07a3b19..4855c3e 100644
--- a/backend/trading_journal/service.py
+++ b/backend/trading_journal/service.py
@@ -250,11 +250,23 @@ def get_cycles_by_user_service(db_session: Session, user_id: int) -> list[CycleR
     return [CycleRead.model_validate(cycle) for cycle in cycles]
 
 
-def _validate_cycle_update_data(cycle_data: CycleUpdate) -> tuple[bool, str]:
+def _validate_cycle_update_data(cycle_data: CycleUpdate) -> tuple[bool, str]:  # noqa: PLR0911
     if cycle_data.status == "CLOSED" and cycle_data.end_date is None:
         return False, "end_date is required when status is CLOSED"
     if cycle_data.status == "OPEN" and cycle_data.end_date is not None:
         return False, "end_date must be empty when status is OPEN"
+    if cycle_data.capital_exposure_cents is not None and cycle_data.capital_exposure_cents < 0:
+        return False, "capital_exposure_cents must be non-negative"
+    if (
+        cycle_data.funding_source is not None
+        and cycle_data.funding_source != "CASH"
+        and (cycle_data.loan_amount_cents is None or cycle_data.loan_interest_rate_tenth_bps is None)
+    ):
+        return False, "loan_amount_cents and loan_interest_rate_tenth_bps are required when funding_source is not CASH"
+    if cycle_data.loan_amount_cents is not None and cycle_data.loan_amount_cents < 0:
+        return False, "loan_amount_cents must be non-negative"
+    if cycle_data.loan_interest_rate_tenth_bps is not None and cycle_data.loan_interest_rate_tenth_bps < 0:
+        return False, "loan_interest_rate_tenth_bps must be non-negative"
     return True, ""