diff --git a/contracts/Cargo.toml b/contracts/Cargo.toml
index a6c082c..e3768cc 100644
--- a/contracts/Cargo.toml
+++ b/contracts/Cargo.toml
@@ -2,6 +2,7 @@
 resolver = "2"
 members = [
     "access_control",
+    "cntr",
     "manage_hub",
     "membership_token",
     "common_types",
diff --git a/contracts/cntr/Cargo.toml b/contracts/cntr/Cargo.toml
new file mode 100644
index 0000000..40fdfbc
--- /dev/null
+++ b/contracts/cntr/Cargo.toml
@@ -0,0 +1,4 @@
+[package]
+name = "cntr"
+version = "0.1.0"
+edition = "2021"
diff --git a/contracts/cntr/src/credit_topup.rs b/contracts/cntr/src/credit_topup.rs
new file mode 100644
index 0000000..f4790bf
--- /dev/null
+++ b/contracts/cntr/src/credit_topup.rs
@@ -0,0 +1,58 @@
+/// Validates a credit top-up operation.
+///
+/// Returns `Ok(new_balance)` when `topup_amount > 0` and
+/// `current_balance + topup_amount <= max_balance`.
+pub fn validate_topup(
+    current_balance: i128,
+    topup_amount: i128,
+    max_balance: i128,
+) -> Result<i128, &'static str> {
+    if topup_amount <= 0 {
+        return Err("Top-up amount must be positive");
+    }
+    let new_balance = current_balance.checked_add(topup_amount).ok_or("Balance would exceed maximum allowed")?;
+    if new_balance > max_balance {
+        return Err("Balance would exceed maximum allowed");
+    }
+    Ok(new_balance)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_valid_topup() {
+        assert_eq!(validate_topup(100, 50, 1000), Ok(150));
+    }
+
+    #[test]
+    fn test_zero_topup_rejected() {
+        assert_eq!(validate_topup(100, 0, 1000), Err("Top-up amount must be positive"));
+    }
+
+    #[test]
+    fn test_negative_topup_rejected() {
+        assert_eq!(validate_topup(100, -10, 1000), Err("Top-up amount must be positive"));
+    }
+
+    #[test]
+    fn test_exact_maximum_boundary() {
+        assert_eq!(validate_topup(900, 100, 1000), Ok(1000));
+    }
+
+    #[test]
+    fn test_one_above_maximum_rejected() {
+        assert_eq!(validate_topup(900, 101, 1000), Err("Balance would exceed maximum allowed"));
+    }
+
+    #[test]
+    fn test_overflow_guard() {
+        assert_eq!(validate_topup(i128::MAX, 1, i128::MAX), Err("Balance would exceed maximum allowed"));
+    }
+
+    #[test]
+    fn test_zero_current_balance() {
+        assert_eq!(validate_topup(0, 500, 1000), Ok(500));
+    }
+}
diff --git a/contracts/cntr/src/lib.rs b/contracts/cntr/src/lib.rs
new file mode 100644
index 0000000..f0def92
--- /dev/null
+++ b/contracts/cntr/src/lib.rs
@@ -0,0 +1,4 @@
+pub mod credit_topup;
+pub mod multi_booking;
+pub mod payment_validator;
+pub mod role_checker;
diff --git a/contracts/cntr/src/multi_booking.rs b/contracts/cntr/src/multi_booking.rs
new file mode 100644
index 0000000..83e970b
--- /dev/null
+++ b/contracts/cntr/src/multi_booking.rs
@@ -0,0 +1,61 @@
+/// Returns the maximum number of simultaneous active bookings allowed for a tier.
+/// Unknown tier strings default to the Bronze limit (2).
+pub fn get_booking_limit(tier: &str) -> u32 {
+    match tier {
+        "Bronze" => 2,
+        "Silver" => 5,
+        "Gold" => 10,
+        "Platinum" => u32::MAX,
+        _ => 2,
+    }
+}
+
+/// Returns true if the member can make another booking given their current active bookings.
+pub fn can_make_booking(tier: &str, current_active_bookings: u32) -> bool {
+    current_active_bookings < get_booking_limit(tier)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_bronze_limit() {
+        assert_eq!(get_booking_limit("Bronze"), 2);
+    }
+
+    #[test]
+    fn test_silver_limit() {
+        assert_eq!(get_booking_limit("Silver"), 5);
+    }
+
+    #[test]
+    fn test_gold_limit() {
+        assert_eq!(get_booking_limit("Gold"), 10);
+    }
+
+    #[test]
+    fn test_platinum_limit() {
+        assert_eq!(get_booking_limit("Platinum"), u32::MAX);
+    }
+
+    #[test]
+    fn test_unknown_tier_defaults_to_bronze() {
+        assert_eq!(get_booking_limit("Diamond"), 2);
+    }
+
+    #[test]
+    fn test_can_make_booking_below_limit() {
+        assert!(can_make_booking("Bronze", 1));
+    }
+
+    #[test]
+    fn test_cannot_make_booking_at_limit() {
+        assert!(!can_make_booking("Bronze", 2));
+    }
+
+    #[test]
+    fn test_cannot_make_booking_above_limit() {
+        assert!(!can_make_booking("Silver", 6));
+    }
+}
diff --git a/contracts/cntr/src/payment_validator.rs b/contracts/cntr/src/payment_validator.rs
new file mode 100644
index 0000000..0ca7a2e
--- /dev/null
+++ b/contracts/cntr/src/payment_validator.rs
@@ -0,0 +1,58 @@
+/// Validates that a received payment amount is within tolerance of the expected amount.
+///
+/// Returns `Ok(())` when `received_stroops >= expected_stroops - tolerance_stroops`.
+pub fn validate_payment_amount(
+    received_stroops: i128,
+    expected_stroops: i128,
+    tolerance_stroops: i128,
+) -> Result<(), &'static str> {
+    if expected_stroops <= 0 {
+        return Err("Expected amount must be positive");
+    }
+    let threshold = expected_stroops.saturating_sub(tolerance_stroops);
+    if received_stroops >= threshold {
+        Ok(())
+    } else {
+        Err("Payment amount insufficient")
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_exact_amount() {
+        assert_eq!(validate_payment_amount(1000, 1000, 0), Ok(()));
+    }
+
+    #[test]
+    fn test_within_tolerance() {
+        assert_eq!(validate_payment_amount(990, 1000, 10), Ok(()));
+    }
+
+    #[test]
+    fn test_one_stroop_below_tolerance() {
+        assert_eq!(validate_payment_amount(989, 1000, 10), Err("Payment amount insufficient"));
+    }
+
+    #[test]
+    fn test_overpayment_accepted() {
+        assert_eq!(validate_payment_amount(1500, 1000, 0), Ok(()));
+    }
+
+    #[test]
+    fn test_zero_expected_rejected() {
+        assert_eq!(validate_payment_amount(0, 0, 0), Err("Expected amount must be positive"));
+    }
+
+    #[test]
+    fn test_negative_expected_rejected() {
+        assert_eq!(validate_payment_amount(100, -1, 0), Err("Expected amount must be positive"));
+    }
+
+    #[test]
+    fn test_underpayment_no_tolerance() {
+        assert_eq!(validate_payment_amount(999, 1000, 0), Err("Payment amount insufficient"));
+    }
+}
diff --git a/contracts/cntr/src/role_checker.rs b/contracts/cntr/src/role_checker.rs
new file mode 100644
index 0000000..d368bd2
--- /dev/null
+++ b/contracts/cntr/src/role_checker.rs
@@ -0,0 +1,41 @@
+use std::collections::HashMap;
+
+/// Simple in-memory role registry for access control.
+#[derive(Default)]
+pub struct RoleRegistry {
+    roles: HashMap<String, Vec<String>>,
+}
+
+impl RoleRegistry {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Grants a role to an address. Idempotent — duplicate grants are ignored.
+    pub fn grant_role(&mut self, address: &str, role: &str) {
+        let roles = self.roles.entry(address.to_string()).or_default();
+        if !roles.contains(&role.to_string()) {
+            roles.push(role.to_string());
+        }
+    }
+
+    /// Revokes a role from an address. No-op if the role is not held.
+    pub fn revoke_role(&mut self, address: &str, role: &str) {
+        if let Some(roles) = self.roles.get_mut(address) {
+            roles.retain(|r| r != role);
+        }
+    }
+
+    /// Returns true if the address holds the given role.
+    pub fn has_role(&self, address: &str, role: &str) -> bool {
+        self.roles
+            .get(address)
+            .map(|roles| roles.contains(&role.to_string()))
+            .unwrap_or(false)
+    }
+
+    /// Returns all roles held by an address.
+    pub fn get_roles(&self, address: &str) -> Vec<String> {
+        self.roles.get(address).cloned().unwrap_or_default()
+    }
+}
diff --git a/contracts/cntr/tests/access_control_tests.rs b/contracts/cntr/tests/access_control_tests.rs
new file mode 100644
index 0000000..16bee39
--- /dev/null
+++ b/contracts/cntr/tests/access_control_tests.rs
@@ -0,0 +1,98 @@
+use cntr::role_checker::RoleRegistry;
+
+#[test]
+fn test_grant_role_to_new_address() {
+    let mut reg = RoleRegistry::new();
+    reg.grant_role("alice", "Admin");
+    assert!(reg.has_role("alice", "Admin"));
+}
+
+#[test]
+fn test_grant_same_role_twice_is_idempotent() {
+    let mut reg = RoleRegistry::new();
+    reg.grant_role("alice", "Admin");
+    reg.grant_role("alice", "Admin");
+    let roles = reg.get_roles("alice");
+    assert_eq!(roles.iter().filter(|r| *r == "Admin").count(), 1);
+}
+
+#[test]
+fn test_grant_two_different_roles_to_same_address() {
+    let mut reg = RoleRegistry::new();
+    reg.grant_role("alice", "Admin");
+    reg.grant_role("alice", "Member");
+    assert!(reg.has_role("alice", "Admin"));
+    assert!(reg.has_role("alice", "Member"));
+}
+
+#[test]
+fn test_revoke_existing_role() {
+    let mut reg = RoleRegistry::new();
+    reg.grant_role("alice", "Admin");
+    reg.revoke_role("alice", "Admin");
+    assert!(!reg.has_role("alice", "Admin"));
+}
+
+#[test]
+fn test_revoke_nonexistent_role_does_not_panic() {
+    let mut reg = RoleRegistry::new();
+    reg.revoke_role("alice", "Admin"); // should not panic
+}
+
+#[test]
+fn test_has_role_for_unknown_address_returns_false() {
+    let reg = RoleRegistry::new();
+    assert!(!reg.has_role("unknown", "Admin"));
+}
+
+#[test]
+fn test_get_all_roles_for_multi_role_holder() {
+    let mut reg = RoleRegistry::new();
+    reg.grant_role("bob", "Admin");
+    reg.grant_role("bob", "Member");
+    reg.grant_role("bob", "Auditor");
+    let roles = reg.get_roles("bob");
+    assert_eq!(roles.len(), 3);
+    assert!(roles.contains(&"Admin".to_string()));
+    assert!(roles.contains(&"Member".to_string()));
+    assert!(roles.contains(&"Auditor".to_string()));
+}
+
+#[test]
+fn test_has_role_with_empty_registry() {
+    let reg = RoleRegistry::new();
+    assert!(!reg.has_role("alice", "Member"));
+}
+
+#[test]
+fn test_revoke_one_role_leaves_others_intact() {
+    let mut reg = RoleRegistry::new();
+    reg.grant_role("carol", "Admin");
+    reg.grant_role("carol", "Member");
+    reg.revoke_role("carol", "Admin");
+    assert!(!reg.has_role("carol", "Admin"));
+    assert!(reg.has_role("carol", "Member"));
+}
+
+#[test]
+fn test_multiple_addresses_independent() {
+    let mut reg = RoleRegistry::new();
+    reg.grant_role("alice", "Admin");
+    reg.grant_role("bob", "Member");
+    assert!(reg.has_role("alice", "Admin"));
+    assert!(!reg.has_role("alice", "Member"));
+    assert!(reg.has_role("bob", "Member"));
+    assert!(!reg.has_role("bob", "Admin"));
+}
+
+#[test]
+fn test_get_roles_returns_empty_for_unknown_address() {
+    let reg = RoleRegistry::new();
+    assert!(reg.get_roles("nobody").is_empty());
+}
+
+#[test]
+fn test_revoke_from_unknown_address_does_not_panic() {
+    let mut reg = RoleRegistry::new();
+    reg.revoke_role("ghost", "Admin"); // should not panic
+}