diff --git a/contracts/split/src/reward_multiplier_ext.rs b/contracts/split/src/reward_multiplier_ext.rs
new file mode 100644
index 0000000..e75c055
--- /dev/null
+++ b/contracts/split/src/reward_multiplier_ext.rs
@@ -0,0 +1,284 @@
+//! Issue #880: recipient reward multiplier system.
+//!
+//! A creator can attach a reward multiplier (in basis points) to one or more
+//! recipients on an invoice. At release time, each recipient's payout is
+//! scaled by `multiplier_bps / 10_000`. The multiplier is capped at 20_000
+//! (2×) and must be ≥ 1 (i.e. zero or negative multipliers are rejected).
+//!
+//! Only the invoice creator may set or clear multipliers. Multipliers can be
+//! updated at any time while the invoice is still `Pending`.
+//!
+//! ## Events
+//! - `(split, mul_set, invoice_id)` — data: `(recipient, multiplier_bps)`
+//! - `(split, mul_clr, invoice_id)` — data: `recipient`
+//!
+//! ## Storage
+//! Uses a local `RewardMulKey` enum stored in **persistent** storage.
+
+use super::*;
+use soroban_sdk::{contractimpl, contracttype, symbol_short, Address, Env, Vec};
+
+/// Maximum multiplier in basis points (2× = 20_000).
+pub const MAX_MULTIPLIER_BPS: u32 = 20_000;
+/// Minimum multiplier in basis points (must be at least 1 bps).
+pub const MIN_MULTIPLIER_BPS: u32 = 1;
+
+/// Persistent storage keys for the reward multiplier module.
+#[contracttype]
+#[derive(Clone)]
+pub enum RewardMulKey {
+    /// `u32` multiplier (in bps) for a specific `(invoice_id, recipient)`.
+    Multiplier(u64, Address),
+    /// `Vec<Address>` — ordered list of recipients that have a multiplier set,
+    /// so `get_all_multipliers` can enumerate them without a full storage scan.
+    MultiplierRecipients(u64),
+}
+
+/// A single entry returned by `get_all_multipliers`.
+#[contracttype]
+#[derive(Clone, Debug, PartialEq)]
+pub struct RecipientMultiplier {
+    pub recipient: Address,
+    /// Multiplier in basis points (10_000 = 1×, 20_000 = 2×).
+    pub multiplier_bps: u32,
+}
+
+// ---------------------------------------------------------------------------
+// Internal helpers
+// ---------------------------------------------------------------------------
+
+fn load_recipients(env: &Env, invoice_id: u64) -> Vec<Address> {
+    env.storage()
+        .persistent()
+        .get(&RewardMulKey::MultiplierRecipients(invoice_id))
+        .unwrap_or_else(|| Vec::new(env))
+}
+
+fn save_recipients(env: &Env, invoice_id: u64, list: &Vec<Address>) {
+    env.storage()
+        .persistent()
+        .set(&RewardMulKey::MultiplierRecipients(invoice_id), list);
+}
+
+/// Returns the effective multiplier for `recipient` on `invoice_id`, or
+/// `10_000` (1×, no-op) if none has been configured.
+pub(crate) fn effective_multiplier(env: &Env, invoice_id: u64, recipient: &Address) -> u32 {
+    env.storage()
+        .persistent()
+        .get(&RewardMulKey::Multiplier(invoice_id, recipient.clone()))
+        .unwrap_or(10_000u32)
+}
+
+// ---------------------------------------------------------------------------
+// Public entry points
+// ---------------------------------------------------------------------------
+
+#[contractimpl]
+impl SplitContract {
+    /// Set a reward multiplier for `recipient` on `invoice_id`.
+    ///
+    /// - Only callable by the invoice creator.
+    /// - Invoice must be in `Pending` status.
+    /// - `multiplier_bps` must be in `[1, 20_000]`.
+    pub fn set_reward_multiplier(
+        env: Env,
+        creator: Address,
+        invoice_id: u64,
+        recipient: Address,
+        multiplier_bps: u32,
+    ) {
+        require_not_paused(&env);
+        creator.require_auth();
+
+        assert!(
+            multiplier_bps >= MIN_MULTIPLIER_BPS && multiplier_bps <= MAX_MULTIPLIER_BPS,
+            "multiplier_bps out of range [1, 20000]"
+        );
+
+        let invoice = load_invoice(&env, invoice_id);
+        assert!(invoice.creator == creator, "only creator can set multiplier");
+        assert!(
+            invoice.status == InvoiceStatus::Pending,
+            "invoice is not pending"
+        );
+        assert!(
+            invoice.recipients.iter().any(|r| r == recipient),
+            "recipient not on invoice"
+        );
+
+        // Track which recipients have a multiplier so we can enumerate them.
+        let mut list = load_recipients(&env, invoice_id);
+        if !list.contains(recipient.clone()) {
+            list.push_back(recipient.clone());
+            save_recipients(&env, invoice_id, &list);
+        }
+
+        env.storage().persistent().set(
+            &RewardMulKey::Multiplier(invoice_id, recipient.clone()),
+            &multiplier_bps,
+        );
+
+        env.events().publish(
+            (symbol_short!("split"), symbol_short!("mul_set"), invoice_id),
+            (recipient, multiplier_bps),
+        );
+    }
+
+    /// Remove the reward multiplier for `recipient` on `invoice_id` (resets
+    /// to the default 1×).
+    ///
+    /// - Only callable by the invoice creator.
+    /// - Invoice must be in `Pending` status.
+    pub fn clear_reward_multiplier(
+        env: Env,
+        creator: Address,
+        invoice_id: u64,
+        recipient: Address,
+    ) {
+        require_not_paused(&env);
+        creator.require_auth();
+
+        let invoice = load_invoice(&env, invoice_id);
+        assert!(invoice.creator == creator, "only creator can clear multiplier");
+        assert!(
+            invoice.status == InvoiceStatus::Pending,
+            "invoice is not pending"
+        );
+
+        env.storage()
+            .persistent()
+            .remove(&RewardMulKey::Multiplier(invoice_id, recipient.clone()));
+
+        // Remove from the enumeration list.
+        let list = load_recipients(&env, invoice_id);
+        let mut new_list = Vec::new(&env);
+        for r in list.iter() {
+            if r != recipient {
+                new_list.push_back(r);
+            }
+        }
+        save_recipients(&env, invoice_id, &new_list);
+
+        env.events().publish(
+            (symbol_short!("split"), symbol_short!("mul_clr"), invoice_id),
+            recipient,
+        );
+    }
+
+    /// Returns the current multiplier (in bps) for `recipient`, or `10_000`
+    /// if none is configured.
+    pub fn get_reward_multiplier(env: Env, invoice_id: u64, recipient: Address) -> u32 {
+        effective_multiplier(&env, invoice_id, &recipient)
+    }
+
+    /// Returns all `(recipient, multiplier_bps)` entries configured for an
+    /// invoice.
+    pub fn get_all_multipliers(env: Env, invoice_id: u64) -> Vec<RecipientMultiplier> {
+        let list = load_recipients(&env, invoice_id);
+        let mut out = Vec::new(&env);
+        for r in list.iter() {
+            let bps: u32 = env
+                .storage()
+                .persistent()
+                .get(&RewardMulKey::Multiplier(invoice_id, r.clone()))
+                .unwrap_or(10_000u32);
+            out.push_back(RecipientMultiplier {
+                recipient: r,
+                multiplier_bps: bps,
+            });
+        }
+        out
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Tests
+// ---------------------------------------------------------------------------
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::ext_test_util::{fixture, mint, new_invoice, pay};
+    use soroban_sdk::testutils::Address as _;
+    use soroban_sdk::Address;
+
+    #[test]
+    fn set_and_get_multiplier() {
+        let f = fixture();
+        let (id, creator, recipient) = new_invoice(&f, 1_000);
+        f.c.set_reward_multiplier(&creator, &id, &recipient, &15_000u32);
+        assert_eq!(f.c.get_reward_multiplier(&id, &recipient), 15_000u32);
+    }
+
+    #[test]
+    fn default_multiplier_is_10000() {
+        let f = fixture();
+        let (id, _, recipient) = new_invoice(&f, 1_000);
+        assert_eq!(f.c.get_reward_multiplier(&id, &recipient), 10_000u32);
+    }
+
+    #[test]
+    fn clear_multiplier_returns_to_default() {
+        let f = fixture();
+        let (id, creator, recipient) = new_invoice(&f, 1_000);
+        f.c.set_reward_multiplier(&creator, &id, &recipient, &15_000u32);
+        f.c.clear_reward_multiplier(&creator, &id, &recipient);
+        assert_eq!(f.c.get_reward_multiplier(&id, &recipient), 10_000u32);
+    }
+
+    #[test]
+    fn get_all_multipliers_lists_entries() {
+        let f = fixture();
+        let (id, creator, recipient) = new_invoice(&f, 1_000);
+        f.c.set_reward_multiplier(&creator, &id, &recipient, &12_000u32);
+        let all = f.c.get_all_multipliers(&id);
+        assert_eq!(all.len(), 1);
+        assert_eq!(all.get(0).unwrap().recipient, recipient);
+        assert_eq!(all.get(0).unwrap().multiplier_bps, 12_000u32);
+    }
+
+    #[test]
+    #[should_panic(expected = "only creator can set multiplier")]
+    fn non_creator_cannot_set_multiplier() {
+        let f = fixture();
+        let (id, _, recipient) = new_invoice(&f, 1_000);
+        let other = Address::generate(&f.env);
+        f.c.set_reward_multiplier(&other, &id, &recipient, &15_000u32);
+    }
+
+    #[test]
+    #[should_panic(expected = "multiplier_bps out of range")]
+    fn zero_multiplier_rejected() {
+        let f = fixture();
+        let (id, creator, recipient) = new_invoice(&f, 1_000);
+        f.c.set_reward_multiplier(&creator, &id, &recipient, &0u32);
+    }
+
+    #[test]
+    #[should_panic(expected = "multiplier_bps out of range")]
+    fn too_large_multiplier_rejected() {
+        let f = fixture();
+        let (id, creator, recipient) = new_invoice(&f, 1_000);
+        f.c.set_reward_multiplier(&creator, &id, &recipient, &20_001u32);
+    }
+
+    #[test]
+    #[should_panic(expected = "recipient not on invoice")]
+    fn unknown_recipient_rejected() {
+        let f = fixture();
+        let (id, creator, _) = new_invoice(&f, 1_000);
+        let stranger = Address::generate(&f.env);
+        f.c.set_reward_multiplier(&creator, &id, &stranger, &15_000u32);
+    }
+
+    #[test]
+    fn multiplier_after_pay_still_readable() {
+        let f = fixture();
+        let (id, creator, recipient) = new_invoice(&f, 100);
+        mint(&f.env, &f.token, &creator, 100);
+        pay(&f, &creator, id, 50);
+        // multiplier on a paid invoice (still Pending until fully funded)
+        f.c.set_reward_multiplier(&creator, &id, &recipient, &11_000u32);
+        assert_eq!(f.c.get_reward_multiplier(&id, &recipient), 11_000u32);
+    }
+}