diff --git a/contracts/invoice-escrow/src/errors.rs b/contracts/invoice-escrow/src/errors.rs
index 38e977d..76b49c2 100644
--- a/contracts/invoice-escrow/src/errors.rs
+++ b/contracts/invoice-escrow/src/errors.rs
@@ -37,4 +37,6 @@ pub enum Error {
     EscrowCancelled = 14,
     /// Payer is not the authorized debtor for this invoice.
     InvalidPayer = 15,
+    /// Due date is invalid (e.g., in the past or zero).
+    InvalidDueDate = 16,
 }
diff --git a/contracts/invoice-escrow/src/lib.rs b/contracts/invoice-escrow/src/lib.rs
index 0004b0a..c3553c0 100644
--- a/contracts/invoice-escrow/src/lib.rs
+++ b/contracts/invoice-escrow/src/lib.rs
@@ -60,6 +60,13 @@ impl InvoiceEscrow {
         if face_value <= 0 || purchase_price <= 0 {
             return Err(Error::InvalidAmount);
         }
+        if due_date == 0 {
+            return Err(Error::InvalidDueDate);
+        }
+        let current_timestamp = env.ledger().timestamp();
+        if due_date <= current_timestamp {
+            return Err(Error::InvalidDueDate);
+        }
         storage::get_config(&env).ok_or(Error::NotInit)?;
         if storage::has_escrow(&env, invoice_id.clone()) {
             return Err(Error::EscrowExists);
diff --git a/contracts/invoice-escrow/src/test.rs b/contracts/invoice-escrow/src/test.rs
index 51901d2..51073af 100644
--- a/contracts/invoice-escrow/src/test.rs
+++ b/contracts/invoice-escrow/src/test.rs
@@ -1976,3 +1976,144 @@ fn test_commitment_persists_through_lifecycle() {
     assert_eq!(escrow_data.commitment, commitment);
     assert_eq!(escrow_data.status, EscrowStatus::Settled);
 }
+
+// ========== Due Date Validation Tests ==========
+
+#[test]
+fn test_create_escrow_due_date_in_past_rejected() {
+    let env = Env::default();
+    env.mock_all_auths();
+
+    let escrow_id = env.register(InvoiceEscrow, ());
+    let escrow_client = InvoiceEscrowClient::new(&env, &escrow_id);
+
+    let admin = Address::generate(&env);
+    let seller = Address::generate(&env);
+    let payment_token = Address::generate(&env);
+    let inv_token = Address::generate(&env);
+
+    escrow_client.initialize(&admin, &300);
+
+    // Set ledger timestamp to a known time
+    env.ledger().with_mut(|li| li.timestamp = 1000000);
+    let current_timestamp = env.ledger().timestamp();
+
+    // Try to create escrow with due_date in the past
+    let past_due_date = current_timestamp - 1000;
+    let result = escrow_client.try_create_escrow(
+        &Symbol::new(&env, "INV_PAST"),
+        &seller,
+        &seller,
+        &1000,
+        &950,
+        &past_due_date,
+        &payment_token,
+        &inv_token,
+        &test_commitment(&env, "past_due_test"),
+    );
+    assert_eq!(result, Err(Ok(Error::InvalidDueDate)));
+}
+
+#[test]
+fn test_create_escrow_due_date_equal_to_current_timestamp_rejected() {
+    let env = Env::default();
+    env.mock_all_auths();
+
+    let escrow_id = env.register(InvoiceEscrow, ());
+    let escrow_client = InvoiceEscrowClient::new(&env, &escrow_id);
+
+    let admin = Address::generate(&env);
+    let seller = Address::generate(&env);
+    let payment_token = Address::generate(&env);
+    let inv_token = Address::generate(&env);
+
+    escrow_client.initialize(&admin, &300);
+
+    // Set ledger timestamp to a known time
+    env.ledger().with_mut(|li| li.timestamp = 1000000);
+    let current_timestamp = env.ledger().timestamp();
+
+    // Try to create escrow with due_date equal to current timestamp
+    let result = escrow_client.try_create_escrow(
+        &Symbol::new(&env, "INV_EQUAL"),
+        &seller,
+        &seller,
+        &1000,
+        &950,
+        &current_timestamp,
+        &payment_token,
+        &inv_token,
+        &test_commitment(&env, "equal_timestamp_test"),
+    );
+    assert_eq!(result, Err(Ok(Error::InvalidDueDate)));
+}
+
+#[test]
+fn test_create_escrow_due_date_zero_rejected() {
+    let env = Env::default();
+    env.mock_all_auths();
+
+    let escrow_id = env.register(InvoiceEscrow, ());
+    let escrow_client = InvoiceEscrowClient::new(&env, &escrow_id);
+
+    let admin = Address::generate(&env);
+    let seller = Address::generate(&env);
+    let payment_token = Address::generate(&env);
+    let inv_token = Address::generate(&env);
+
+    escrow_client.initialize(&admin, &300);
+
+    // Try to create escrow with due_date = 0
+    let result = escrow_client.try_create_escrow(
+        &Symbol::new(&env, "INV_ZERO"),
+        &seller,
+        &seller,
+        &1000,
+        &950,
+        &0,
+        &payment_token,
+        &inv_token,
+        &test_commitment(&env, "zero_due_date_test"),
+    );
+    assert_eq!(result, Err(Ok(Error::InvalidDueDate)));
+}
+
+#[test]
+fn test_create_escrow_due_date_in_future_accepted() {
+    let env = Env::default();
+    env.mock_all_auths();
+
+    let escrow_id = env.register(InvoiceEscrow, ());
+    let escrow_client = InvoiceEscrowClient::new(&env, &escrow_id);
+
+    let admin = Address::generate(&env);
+    let seller = Address::generate(&env);
+    let payment_token = Address::generate(&env);
+    let inv_token = Address::generate(&env);
+
+    escrow_client.initialize(&admin, &300);
+
+    // Set ledger timestamp to a known time
+    env.ledger().with_mut(|li| li.timestamp = 1000000);
+    let current_timestamp = env.ledger().timestamp();
+
+    // Create escrow with due_date in the future - should succeed
+    let future_due_date = current_timestamp + 1000000;
+    let invoice_id = Symbol::new(&env, "INV_FUTURE");
+    escrow_client.create_escrow(
+        &invoice_id,
+        &seller,
+        &seller,
+        &1000,
+        &950,
+        &future_due_date,
+        &payment_token,
+        &inv_token,
+        &test_commitment(&env, "future_due_test"),
+    );
+
+    // Verify escrow was created successfully
+    let escrow_data = escrow_client.get_escrow(&invoice_id);
+    assert_eq!(escrow_data.due_dt, future_due_date);
+    assert_eq!(escrow_data.status, EscrowStatus::Created);
+}
diff --git a/contracts/invoice-token/src/lib.rs b/contracts/invoice-token/src/lib.rs
index 2f136bf..ab77e99 100644
--- a/contracts/invoice-token/src/lib.rs
+++ b/contracts/invoice-token/src/lib.rs
@@ -114,6 +114,9 @@ impl InvoiceToken {
         expiration_ledger: u32,
     ) -> Result<(), Error> {
         from.require_auth();
+        if amount < 0 {
+            return Err(Error::InvalidAmount);
+        }
         let ledger = env.ledger().sequence();
         if amount != 0 && expiration_ledger < ledger {
             return Err(Error::InvalidExpiration);
diff --git a/contracts/invoice-token/src/test.rs b/contracts/invoice-token/src/test.rs
index 2782aec..ca441bc 100644
--- a/contracts/invoice-token/src/test.rs
+++ b/contracts/invoice-token/src/test.rs
@@ -1037,3 +1037,60 @@ fn test_approve_update_expiration_shortens() {
         .with_mut(|li| li.sequence_number = new_expiration + 1);
     assert_eq!(client.allowance(&admin, &spender), 0);
 }
+
+// ========== Negative Amount Tests ==========
+
+#[test]
+fn test_approve_negative_amount_rejected() {
+    let env = Env::default();
+    env.mock_all_auths();
+    let (client, admin, _minter) = setup_token(&env);
+
+    let spender = Address::generate(&env);
+    let expiration = env.ledger().sequence() + 100;
+
+    // Attempt to approve with negative amount should fail
+    let result = client.try_approve(&admin, &spender, &(-100i128), &expiration);
+    assert_eq!(result, Err(Ok(crate::errors::Error::InvalidAmount)));
+
+    // Verify no allowance was set
+    assert_eq!(client.allowance(&admin, &spender), 0);
+}
+
+#[test]
+fn test_approve_zero_amount_accepted() {
+    let env = Env::default();
+    env.mock_all_auths();
+    let (client, admin, _minter) = setup_token(&env);
+
+    let spender = Address::generate(&env);
+    let expiration = env.ledger().sequence() + 100;
+
+    // First set a non-zero allowance
+    client.approve(&admin, &spender, &500, &expiration);
+    assert_eq!(client.allowance(&admin, &spender), 500);
+
+    // Approve with zero amount should remove allowance (current behavior)
+    client.approve(&admin, &spender, &0, &expiration);
+    assert_eq!(client.allowance(&admin, &spender), 0);
+}
+
+#[test]
+fn test_approve_positive_amount_invalid_expiration_rejected() {
+    let env = Env::default();
+    env.mock_all_auths();
+    let (client, admin, _minter) = setup_token(&env);
+
+    let spender = Address::generate(&env);
+
+    // Advance ledger to ensure we can test past expiration
+    env.ledger().with_mut(|li| li.sequence_number = 10);
+    let current_ledger = env.ledger().sequence();
+
+    // Attempt to approve with positive amount and invalid expiration should fail
+    let result = client.try_approve(&admin, &spender, &500, &(current_ledger - 1));
+    assert_eq!(result, Err(Ok(crate::errors::Error::InvalidExpiration)));
+
+    // Verify no allowance was set
+    assert_eq!(client.allowance(&admin, &spender), 0);
+}
diff --git a/docs/API.md b/docs/API.md
index 33f39c0..ec8769c 100644
--- a/docs/API.md
+++ b/docs/API.md
@@ -30,7 +30,22 @@ Returns the current administrative address of the contract.
 (Legacy documentation for reference)
 
 ### `initialize(admin: Address, platform_fee_bps: u32)`
-### `create_escrow(invoice_id: Symbol, seller: Address, amount: i128, due_date: u64, payment_token: Address, invoice_token: Address)`
+### `create_escrow(invoice_id: Symbol, seller: Address, debtor: Address, face_value: i128, purchase_price: i128, due_date: u64, payment_token: Address, invoice_token: Address, commitment: BytesN<32>)`
+Creates an escrow for an invoice with the specified parameters.
+- **invoice_id**: Unique identifier for the invoice.
+- **seller**: Address of the invoice seller (creator of the escrow).
+- **debtor**: Address of the party responsible for paying the invoice.
+- **face_value**: Total amount owed by the debtor (must be > 0).
+- **purchase_price**: Amount the investor will pay to fund the escrow (must be > 0).
+- **due_date**: Unix timestamp when the invoice is due (must be > 0 and > current ledger timestamp).
+- **payment_token**: Address of the token used for payments.
+- **invoice_token**: Address of the invoice token contract.
+- **commitment**: SHA-256 hash of off-chain invoice data (immutable anchor).
+
+**Constraints:**
+- face_value and purchase_price must be positive (> 0)
+- due_date must be non-zero and strictly greater than the current ledger timestamp
+- Each invoice_id can only be used once
 ### `fund_escrow(invoice_id: Symbol, buyer: Address)`
 ### `record_payment(invoice_id: Symbol, payer: Address, amount: i128)`
 Records a full or partial payment for a funded invoice.