diff --git a/contracts/split/src/lib.rs b/contracts/split/src/lib.rs
index 6f82aef..768ed87 100644
--- a/contracts/split/src/lib.rs
+++ b/contracts/split/src/lib.rs
@@ -410,6 +410,19 @@ fn load_treasury_record(env: &Env, group_id: u64) -> TreasuryRecord {
         .expect("treasury record not found")
 }
 
+fn save_invoice_ext(env: &Env, id: u64, ext: &InvoiceExt) {
+    env.storage()
+        .persistent()
+        .set(&invoice_ext_key(id), ext);
+}
+
+fn load_invoice_ext(env: &Env, id: u64) -> InvoiceExt {
+    env.storage()
+        .persistent()
+        .get(&invoice_ext_key(id))
+        .expect("invoice extension not found")
+}
+
 // ---------------------------------------------------------------------------
 // Contract
 // ---------------------------------------------------------------------------
@@ -4041,4 +4054,89 @@ impl SplitContract {
             save_invoice(&env, invoice_id, &invoice);
         }
     }
+
+    fn enforce_payment_limits(
+        env: &Env,
+        invoice_id: u64,
+        payer: &Address,
+        ext: &InvoiceExt,
+        now: u64,
+    ) {
+        if let Some(cooldown_secs) = ext.payment_cooldown_secs {
+            let last_payment: Option<u64> = env
+                .storage()
+                .persistent()
+                .get(&payer_cooldown_key(invoice_id, payer.clone()));
+
+            if let Some(last_payment_at) = last_payment {
+                assert!(
+                    last_payment_at.saturating_add(cooldown_secs) <= now,
+                    "payment cooldown active"
+                );
+            }
+        }
+
+        if let (Some(max_payments), Some(window_secs)) =
+            (ext.max_payments_per_window, ext.payment_window_secs)
+        {
+            let recent = Self::active_payment_window(env, invoice_id, now, window_secs);
+            assert!(
+                recent.len() < max_payments,
+                "payment rate limit exceeded"
+            );
+        }
+    }
+
+    fn record_payment_limits(
+        env: &Env,
+        invoice_id: u64,
+        payer: &Address,
+        ext: &InvoiceExt,
+        now: u64,
+    ) {
+        if ext.payment_cooldown_secs.is_some() {
+            env.storage()
+                .persistent()
+                .set(&payer_cooldown_key(invoice_id, payer.clone()), &now);
+        }
+
+        if let (Some(_), Some(window_secs)) =
+            (ext.max_payments_per_window, ext.payment_window_secs)
+        {
+            let mut recent = Self::active_payment_window(env, invoice_id, now, window_secs);
+            while recent.len() >= PAYMENT_WINDOW_CAP {
+                recent.pop_front();
+            }
+            recent.push_back(now);
+            env.storage()
+                .persistent()
+                .set(&payment_window_key(invoice_id), &recent);
+        }
+    }
+
+    fn active_payment_window(
+        env: &Env,
+        invoice_id: u64,
+        now: u64,
+        window_secs: u64,
+    ) -> Vec<u64> {
+        let stored: Vec<u64> = env
+            .storage()
+            .persistent()
+            .get(&payment_window_key(invoice_id))
+            .unwrap_or(Vec::new(env));
+        let mut active = Vec::new(env);
+
+        for paid_at in stored.iter() {
+            if paid_at.saturating_add(window_secs) > now {
+                active.push_back(paid_at);
+            }
+        }
+
+        while active.len() > PAYMENT_WINDOW_CAP {
+            active.pop_front();
+        }
+
+        active
+    }
 }
diff --git a/contracts/split/src/test.rs b/contracts/split/src/test.rs
index 0213e92..daa4961 100644
--- a/contracts/split/src/test.rs
+++ b/contracts/split/src/test.rs
@@ -4177,3 +4177,109 @@ fn test_min_funding_amount_releases_when_met() {
     assert_eq!(invoice.funded, 100);
     assert_eq!(invoice.status, InvoiceStatus::Released);
 }
+
+#[test]
+#[should_panic(expected = "payment cooldown active")]
+fn test_cooldown_blocks_same_payer_within_window() {
+    let (env, contract_id, token_id) = setup();
+    let c = client(&env, &contract_id);
+    let stellar_asset = StellarAssetClient::new(&env, &token_id);
+
+    let payer = Address::generate(&env);
+    let other_payer = Address::generate(&env);
+    stellar_asset.mint(&payer, &500);
+    stellar_asset.mint(&other_payer, &500);
+
+    env.ledger().set_timestamp(1_000);
+    let id = single_recipient_invoice(
+        &env,
+        &c,
+        &token_id,
+        500,
+        invoice_options(Some(60), None, None),
+    );
+
+    c.pay(&payer, &id, &100_i128);
+    c.pay(&other_payer, &id, &100_i128);
+    c.pay(&payer, &id, &100_i128);
+}
+
+#[test]
+#[should_panic(expected = "payment rate limit exceeded")]
+fn test_rate_limit_blocks_after_n_payments() {
+    let (env, contract_id, token_id) = setup();
+    let c = client(&env, &contract_id);
+    let stellar_asset = StellarAssetClient::new(&env, &token_id);
+
+    env.ledger().set_timestamp(1_000);
+    let id = single_recipient_invoice(
+        &env,
+        &c,
+        &token_id,
+        500,
+        invoice_options(None, Some(2), Some(60)),
+    );
+
+    for _ in 0..3 {
+        let payer = Address::generate(&env);
+        stellar_asset.mint(&payer, &100);
+        c.pay(&payer, &id, &100_i128);
+    }
+}
+
+#[test]
+fn test_rate_limit_window_resets() {
+    let (env, contract_id, token_id) = setup();
+    let c = client(&env, &contract_id);
+    let stellar_asset = StellarAssetClient::new(&env, &token_id);
+
+    env.ledger().set_timestamp(1_000);
+    let id = single_recipient_invoice(
+        &env,
+        &c,
+        &token_id,
+        500,
+        invoice_options(None, Some(2), Some(60)),
+    );
+
+    for _ in 0..2 {
+        let payer = Address::generate(&env);
+        stellar_asset.mint(&payer, &100);
+        c.pay(&payer, &id, &100_i128);
+    }
+
+    env.ledger().set_timestamp(1_061);
+    let payer = Address::generate(&env);
+    stellar_asset.mint(&payer, &100);
+    c.pay(&payer, &id, &100_i128);
+}
+
+#[test]
+#[should_panic(expected = "payment rate limit exceeded")]
+fn test_cooldown_and_rate_limit_independent() {
+    let (env, contract_id, token_id) = setup();
+    let c = client(&env, &contract_id);
+    let stellar_asset = StellarAssetClient::new(&env, &token_id);
+
+    let payer = Address::generate(&env);
+    let other_payer = Address::generate(&env);
+    stellar_asset.mint(&payer, &500);
+    stellar_asset.mint(&other_payer, &500);
+
+    env.ledger().set_timestamp(1_000);
+    let id = single_recipient_invoice(
+        &env,
+        &c,
+        &token_id,
+        500,
+        invoice_options(Some(120), Some(1), Some(60)),
+    );
+
+    let ext = c.get_invoice_ext(&id);
+    assert_eq!(ext.payment_cooldown_secs, Some(120));
+    assert_eq!(ext.max_payments_per_window, Some(1));
+    assert_eq!(ext.payment_window_secs, Some(60));
+
+    c.pay(&payer, &id, &100_i128);
+    c.pay(&other_payer, &id, &100_i128);
+}
diff --git a/contracts/split/src/types.rs b/contracts/split/src/types.rs
index d251307..7542623 100644
--- a/contracts/split/src/types.rs
+++ b/contracts/split/src/types.rs
@@ -607,3 +607,28 @@ impl Invoice {
         }
     }
 }
+
+impl From<InvoiceOptions> for InvoiceExt {
+    fn from(options: InvoiceOptions) -> Self {
+        Self {
+            payment_cooldown_secs: options.payment_cooldown_secs,
+            max_payments_per_window: options.max_payments_per_window,
+            payment_window_secs: options.payment_window_secs,
+        }
+    }
+}
+
+impl From<InvoiceCore> for Invoice {
+    fn from(core: InvoiceCore) -> Self {
+        Self {
+            creator: core.creator,
+            recipients: core.recipients,
+            amounts: core.amounts,
+            token: core.token,
+            deadline: core.deadline,
+            funded: core.funded,
+            status: core.status,
+            payments: core.payments,
+        }
+    }
+}