diff --git a/contracts/sorosave/src/contribution.rs b/contracts/sorosave/src/contribution.rs
index 4285c9f..4a56a48 100644
--- a/contracts/sorosave/src/contribution.rs
+++ b/contracts/sorosave/src/contribution.rs
@@ -2,7 +2,9 @@ use soroban_sdk::{Address, Env};
 
 use crate::errors::ContractError;
 use crate::storage;
-use crate::types::{GroupStatus, RoundInfo};
+use crate::types::{ContributionType, GroupStatus, RoundInfo};
+
+const BASIS_POINTS_DENOMINATOR: i128 = 10_000;
 
 pub fn contribute(env: &Env, member: Address, group_id: u64) -> Result<(), ContractError> {
     member.require_auth();
@@ -37,17 +39,30 @@ pub fn contribute(env: &Env, member: Address, group_id: u64) -> Result<(), Contr
         return Err(ContractError::AlreadyContributed);
     }
 
+    let contribution_amount = match group.contribution_type {
+        ContributionType::Fixed => group.contribution_amount,
+        ContributionType::Percentage => {
+            let base_amount = storage::get_member_base_amount(env, group_id, &member)
+                .ok_or(ContractError::BaseAmountRequired)?;
+            let amount = (base_amount * group.contribution_amount) / BASIS_POINTS_DENOMINATOR;
+            if amount <= 0 {
+                return Err(ContractError::InvalidAmount);
+            }
+            amount
+        }
+    };
+
     // Transfer tokens from member to this contract
     let token_client = soroban_sdk::token::Client::new(env, &group.token);
     token_client.transfer(
         &member,
         &env.current_contract_address(),
-        &group.contribution_amount,
+        &contribution_amount,
     );
 
     // Record contribution
     round_info.contributions.set(member.clone(), true);
-    round_info.total_contributed += group.contribution_amount;
+    round_info.total_contributed += contribution_amount;
 
     // Check if all members have contributed
     if round_info.contributions.len() == group.members.len() {
@@ -58,7 +73,7 @@ pub fn contribute(env: &Env, member: Address, group_id: u64) -> Result<(), Contr
 
     env.events().publish(
         (crate::symbol_short!("contrib"),),
-        (group_id, member, group.contribution_amount),
+        (group_id, member, contribution_amount),
     );
 
     Ok(())
diff --git a/contracts/sorosave/src/errors.rs b/contracts/sorosave/src/errors.rs
index a2b9d9d..bff0038 100644
--- a/contracts/sorosave/src/errors.rs
+++ b/contracts/sorosave/src/errors.rs
@@ -22,4 +22,5 @@ pub enum ContractError {
     InsufficientMembers = 16,
     RoundNotComplete = 17,
     GroupCompleted = 18,
+    BaseAmountRequired = 19,
 }
diff --git a/contracts/sorosave/src/group.rs b/contracts/sorosave/src/group.rs
index 5033347..5720c14 100644
--- a/contracts/sorosave/src/group.rs
+++ b/contracts/sorosave/src/group.rs
@@ -2,7 +2,9 @@ use soroban_sdk::{Address, Env, Map, String, Vec};
 
 use crate::errors::ContractError;
 use crate::storage;
-use crate::types::{GroupStatus, RoundInfo, SavingsGroup};
+use crate::types::{ContributionType, GroupStatus, RoundInfo, SavingsGroup};
+
+const MAX_PERCENTAGE_BPS: i128 = 10_000;
 
 pub fn create_group(
     env: &Env,
@@ -12,12 +14,38 @@ pub fn create_group(
     contribution_amount: i128,
     cycle_length: u64,
     max_members: u32,
+) -> Result<u64, ContractError> {
+    create_group_with_type(
+        env,
+        admin,
+        name,
+        token,
+        contribution_amount,
+        ContributionType::Fixed,
+        cycle_length,
+        max_members,
+    )
+}
+
+pub fn create_group_with_type(
+    env: &Env,
+    admin: Address,
+    name: String,
+    token: Address,
+    contribution_amount: i128,
+    contribution_type: ContributionType,
+    cycle_length: u64,
+    max_members: u32,
 ) -> Result<u64, ContractError> {
     admin.require_auth();
 
     if contribution_amount <= 0 {
         return Err(ContractError::InvalidAmount);
     }
+    if contribution_type == ContributionType::Percentage && contribution_amount > MAX_PERCENTAGE_BPS
+    {
+        return Err(ContractError::InvalidAmount);
+    }
     if max_members < 2 {
         return Err(ContractError::InsufficientMembers);
     }
@@ -33,6 +61,7 @@ pub fn create_group(
         name,
         admin: admin.clone(),
         token,
+        contribution_type,
         contribution_amount,
         cycle_length,
         max_members,
@@ -83,6 +112,69 @@ pub fn join_group(env: &Env, member: Address, group_id: u64) -> Result<(), Contr
     Ok(())
 }
 
+pub fn set_member_base_amount(
+    env: &Env,
+    member: Address,
+    group_id: u64,
+    base_amount: i128,
+) -> Result<(), ContractError> {
+    member.require_auth();
+
+    if base_amount <= 0 {
+        return Err(ContractError::InvalidAmount);
+    }
+
+    let group = storage::get_group(env, group_id).ok_or(ContractError::GroupNotFound)?;
+
+    if group.status != GroupStatus::Forming {
+        return Err(ContractError::GroupNotForming);
+    }
+    if group.contribution_type != ContributionType::Percentage {
+        return Err(ContractError::InvalidAmount);
+    }
+
+    let mut is_member = false;
+    for existing_member in group.members.iter() {
+        if existing_member == member {
+            is_member = true;
+            break;
+        }
+    }
+    if !is_member {
+        return Err(ContractError::NotMember);
+    }
+
+    storage::set_member_base_amount(env, group_id, &member, base_amount);
+
+    env.events().publish(
+        (crate::symbol_short!("base_set"),),
+        (group_id, member, base_amount),
+    );
+
+    Ok(())
+}
+
+pub fn get_member_base_amount(
+    env: &Env,
+    member: Address,
+    group_id: u64,
+) -> Result<i128, ContractError> {
+    let group = storage::get_group(env, group_id).ok_or(ContractError::GroupNotFound)?;
+
+    let mut is_member = false;
+    for existing_member in group.members.iter() {
+        if existing_member == member {
+            is_member = true;
+            break;
+        }
+    }
+    if !is_member {
+        return Err(ContractError::NotMember);
+    }
+
+    storage::get_member_base_amount(env, group_id, &member).ok_or(ContractError::BaseAmountRequired)
+}
+
 pub fn leave_group(env: &Env, member: Address, group_id: u64) -> Result<(), ContractError> {
     member.require_auth();
 
@@ -114,6 +206,7 @@ pub fn leave_group(env: &Env, member: Address, group_id: u64) -> Result<(), Cont
     group.members = new_members;
     storage::set_group(env, &group);
     storage::remove_member_group(env, &member, group_id);
+    storage::remove_member_base_amount(env, group_id, &member);
 
     env.events()
         .publish((crate::symbol_short!("grp_leav"),), (group_id, member));
@@ -137,6 +230,13 @@ pub fn start_group(env: &Env, admin: Address, group_id: u64) -> Result<(), Contr
     if group.members.len() < 2 {
         return Err(ContractError::InsufficientMembers);
     }
+    if group.contribution_type == ContributionType::Percentage {
+        for member in group.members.iter() {
+            if storage::get_member_base_amount(env, group_id, &member).is_none() {
+                return Err(ContractError::BaseAmountRequired);
+            }
+        }
+    }
 
     // Set payout order to member join order (can be randomized later)
     group.payout_order = group.members.clone();
diff --git a/contracts/sorosave/src/lib.rs b/contracts/sorosave/src/lib.rs
index 454a6ca..b3ef25a 100644
--- a/contracts/sorosave/src/lib.rs
+++ b/contracts/sorosave/src/lib.rs
@@ -49,11 +49,53 @@ impl SoroSaveContract {
         )
     }
 
+    /// Create a new savings group with an explicit contribution model.
+    pub fn create_group_with_type(
+        env: Env,
+        admin: Address,
+        name: String,
+        token: Address,
+        contribution_amount: i128,
+        contribution_type: ContributionType,
+        cycle_length: u64,
+        max_members: u32,
+    ) -> Result<u64, ContractError> {
+        group::create_group_with_type(
+            &env,
+            admin,
+            name,
+            token,
+            contribution_amount,
+            contribution_type,
+            cycle_length,
+            max_members,
+        )
+    }
+
     /// Join an existing group that is still forming.
     pub fn join_group(env: Env, member: Address, group_id: u64) -> Result<(), ContractError> {
         group::join_group(&env, member, group_id)
     }
 
+    /// Set a member's base amount for percentage-based groups while still forming.
+    pub fn set_member_base_amount(
+        env: Env,
+        member: Address,
+        group_id: u64,
+        base_amount: i128,
+    ) -> Result<(), ContractError> {
+        group::set_member_base_amount(&env, member, group_id, base_amount)
+    }
+
+    /// Get a member's declared base amount for a group.
+    pub fn get_member_base_amount(
+        env: Env,
+        member: Address,
+        group_id: u64,
+    ) -> Result<i128, ContractError> {
+        group::get_member_base_amount(&env, member, group_id)
+    }
+
     /// Leave a group (only allowed while group is still forming).
     pub fn leave_group(env: Env, member: Address, group_id: u64) -> Result<(), ContractError> {
         group::leave_group(&env, member, group_id)
diff --git a/contracts/sorosave/src/storage.rs b/contracts/sorosave/src/storage.rs
index 3f24bc8..7b9a6bb 100644
--- a/contracts/sorosave/src/storage.rs
+++ b/contracts/sorosave/src/storage.rs
@@ -103,6 +103,28 @@ pub fn remove_member_group(env: &Env, member: &Address, group_id: u64) {
     extend_persistent_ttl(env, &key);
 }
 
+// --- Member Base Amounts ---
+
+pub fn get_member_base_amount(env: &Env, group_id: u64, member: &Address) -> Option<i128> {
+    let key = DataKey::MemberBaseAmount(group_id, member.clone());
+    let result = env.storage().persistent().get(&key);
+    if result.is_some() {
+        extend_persistent_ttl(env, &key);
+    }
+    result
+}
+
+pub fn set_member_base_amount(env: &Env, group_id: u64, member: &Address, base_amount: i128) {
+    let key = DataKey::MemberBaseAmount(group_id, member.clone());
+    env.storage().persistent().set(&key, &base_amount);
+    extend_persistent_ttl(env, &key);
+}
+
+pub fn remove_member_base_amount(env: &Env, group_id: u64, member: &Address) {
+    let key = DataKey::MemberBaseAmount(group_id, member.clone());
+    env.storage().persistent().remove(&key);
+}
+
 // --- Dispute ---
 
 #[allow(dead_code)]
diff --git a/contracts/sorosave/src/test.rs b/contracts/sorosave/src/test.rs
index f1ac1ef..88f8924 100644
--- a/contracts/sorosave/src/test.rs
+++ b/contracts/sorosave/src/test.rs
@@ -1,6 +1,10 @@
-use soroban_sdk::{testutils::Address as _, token::StellarAssetClient, Address, Env, String};
+use soroban_sdk::{
+    testutils::Address as _,
+    token::{Client as TokenClient, StellarAssetClient},
+    Address, Env, String,
+};
 
-use crate::types::GroupStatus;
+use crate::types::{ContributionType, GroupStatus};
 use crate::{SoroSaveContract, SoroSaveContractClient};
 
 fn setup_env() -> (Env, Address, SoroSaveContractClient<'static>, Address) {
@@ -46,6 +50,7 @@ fn test_create_group() {
 
     let group = client.get_group(&group_id);
     assert_eq!(group.admin, admin);
+    assert_eq!(group.contribution_type, ContributionType::Fixed);
     assert_eq!(group.contribution_amount, 1_000_000);
     assert_eq!(group.max_members, 5);
     assert_eq!(group.status, GroupStatus::Forming);
@@ -222,3 +227,49 @@ fn test_set_group_admin() {
     let group = client.get_group(&group_id);
     assert_eq!(group.admin, new_admin);
 }
+
+#[test]
+fn test_percentage_group_dynamic_pot() {
+    let (env, admin, client, _token) = setup_env();
+
+    let token_admin = Address::generate(&env);
+    let token_id = env.register_stellar_asset_contract_v2(token_admin.clone());
+    let token_client = StellarAssetClient::new(&env, &token_id.address());
+    let token_reader = TokenClient::new(&env, &token_id.address());
+
+    let member1 = Address::generate(&env);
+    token_client.mint(&admin, &20_000_000);
+    token_client.mint(&member1, &20_000_000);
+
+    let group_id = client.create_group_with_type(
+        &admin,
+        &String::from_str(&env, "Percentage Group"),
+        &token_id.address(),
+        &1_000, // 10.00% in basis points
+        &ContributionType::Percentage,
+        &86400,
+        &5,
+    );
+
+    client.join_group(&member1, &group_id);
+    client.set_member_base_amount(&admin, &group_id, &5_000_000);
+    client.set_member_base_amount(&member1, &group_id, &10_000_000);
+
+    assert_eq!(client.get_member_base_amount(&admin, &group_id), 5_000_000);
+    assert_eq!(
+        client.get_member_base_amount(&member1, &group_id),
+        10_000_000
+    );
+
+    client.start_group(&admin, &group_id);
+    client.contribute(&admin, &group_id);
+    client.contribute(&member1, &group_id);
+
+    let round = client.get_round_status(&group_id, &1);
+    assert!(round.is_complete);
+    assert_eq!(round.total_contributed, 1_500_000);
+
+    client.distribute_payout(&group_id);
+    assert_eq!(token_reader.balance(&admin), 21_000_000);
+    assert_eq!(token_reader.balance(&member1), 19_000_000);
+}
diff --git a/contracts/sorosave/src/types.rs b/contracts/sorosave/src/types.rs
index f741099..6a5693d 100644
--- a/contracts/sorosave/src/types.rs
+++ b/contracts/sorosave/src/types.rs
@@ -1,5 +1,13 @@
 use soroban_sdk::{contracttype, Address, Map, String, Vec};
 
+/// Contribution model used by a savings group.
+#[contracttype]
+#[derive(Clone, Debug, PartialEq)]
+pub enum ContributionType {
+    Fixed,
+    Percentage,
+}
+
 /// Status of a savings group throughout its lifecycle.
 #[contracttype]
 #[derive(Clone, Debug, PartialEq)]
@@ -19,6 +27,7 @@ pub struct SavingsGroup {
     pub name: String,
     pub admin: Address,
     pub token: Address,
+    pub contribution_type: ContributionType,
     pub contribution_amount: i128,
     pub cycle_length: u64,
     pub max_members: u32,
@@ -60,5 +69,6 @@ pub enum DataKey {
     Group(u64),
     Round(u64, u32),
     MemberGroups(Address),
+    MemberBaseAmount(u64, Address),
     Dispute(u64),
 }