diff --git a/src/main/java/longah/exception/ExceptionMessage.java b/src/main/java/longah/exception/ExceptionMessage.java
index 4762c0cc65..0a2b90cf08 100644
--- a/src/main/java/longah/exception/ExceptionMessage.java
+++ b/src/main/java/longah/exception/ExceptionMessage.java
@@ -6,9 +6,10 @@ public enum ExceptionMessage {
     INVALID_INDEX ("Invalid index."),
     // Member Exceptions
     DUPLICATE_MEMBER ("Duplicate member."),
+    INVALID_MEMBER_NAME ("Invalid member name."),
+    MEMBER_NOT_FOUND ("Member not found."),
     // Transaction Exceptions
     INVALID_TRANSACTION_FORMAT ("Invalid transaction format."),
-    INVALID_MEMBER_NAME ("Invalid member name."),
     INVALID_TRANSACTION_VALUE ("Invalid transaction value."),
     INVALID_VALUE_FORMAT ("Invalid value format."),
     // Data Storage Exceptions
diff --git a/src/main/java/longah/node/Member.java b/src/main/java/longah/node/Member.java
index dbd5fc5c02..4745fca570 100644
--- a/src/main/java/longah/node/Member.java
+++ b/src/main/java/longah/node/Member.java
@@ -1,5 +1,10 @@
 package longah.node;
 
+import java.util.regex.Pattern;
+
+import longah.exception.LongAhException;
+import longah.exception.ExceptionMessage;
+
 /**
  * Represents a member in the LongAh application.
  */
@@ -11,8 +16,14 @@ public class Member {
      * Constructs a new Member instance with the given name and zero balance.
      *
      * @param name The name of the member.
+     * @throws LongAhException If the name is invalid.
      */
-    public Member(String name) {
+    public Member(String name) throws LongAhException {
+        // Check if name is fully alphanumeric
+        if (!Pattern.matches("[A-Za-z0-9]+", name)) {
+            throw new LongAhException(ExceptionMessage.INVALID_MEMBER_NAME);
+        }
+
         this.name = name;
         this.balance = 0.0;
     }
@@ -22,7 +33,10 @@ public Member(String name) {
      *
      * @param amount The amount to add to the balance.
      */
-    public void addToBalance(double amount) {
+    public void addToBalance(double amount) throws LongAhException {
+        if (amount <= 0) {
+            throw new LongAhException(ExceptionMessage.INVALID_TRANSACTION_VALUE);
+        }
         this.balance += amount;
     }
 
@@ -31,7 +45,10 @@ public void addToBalance(double amount) {
      *
      * @param amount The amount to subtract from the balance.
      */
-    public void subtractFromBalance(double amount) {
+    public void subtractFromBalance(double amount) throws LongAhException {
+        if (amount <= 0) {
+            throw new LongAhException(ExceptionMessage.INVALID_TRANSACTION_VALUE);
+        }
         this.balance -= amount;
     }
 
diff --git a/src/main/java/longah/node/Transaction.java b/src/main/java/longah/node/Transaction.java
index def28ebb26..98f438ba7d 100644
--- a/src/main/java/longah/node/Transaction.java
+++ b/src/main/java/longah/node/Transaction.java
@@ -80,7 +80,7 @@ public Double addPayee(String expression, MemberList memberList) throws LongAhEx
     /**
      * Updates the balances of the members involved in the transaction.
      */
-    public void updateBalances() {
+    public void updateBalances() throws LongAhException {
         for (HashMap.Entry<Member, Double> entry : this.subtransactions.entrySet()) {
             Member member = entry.getKey();
             double amount = entry.getValue();
diff --git a/src/main/java/longah/util/MemberList.java b/src/main/java/longah/util/MemberList.java
index 8e891391eb..83a55da3a9 100644
--- a/src/main/java/longah/util/MemberList.java
+++ b/src/main/java/longah/util/MemberList.java
@@ -68,7 +68,7 @@ public Member getMember(String name) throws LongAhException {
                 return member;
             }
         }
-        throw new LongAhException(ExceptionMessage.INVALID_MEMBER_NAME);
+        throw new LongAhException(ExceptionMessage.MEMBER_NOT_FOUND);
     }
 
     /**
diff --git a/src/test/java/longah/node/MemberTest.java b/src/test/java/longah/node/MemberTest.java
new file mode 100644
index 0000000000..8c90fefa49
--- /dev/null
+++ b/src/test/java/longah/node/MemberTest.java
@@ -0,0 +1,32 @@
+package longah.node;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.fail;
+
+import longah.exception.ExceptionMessage;
+
+public class MemberTest {
+    @Test
+    public void memberConstructor_validName_success() {
+        try {
+            Member member = new Member("Alice");
+            assertEquals("Alice", member.getName());
+            assertEquals(0.0, member.getBalance());
+        } catch (Exception e) {
+            fail();
+        }
+    }
+
+    @Test
+    public void memberConstructor_invalidName_exceptionThrown() {
+        try {
+            new Member("Alice123-");
+            fail();
+        } catch (Exception e) {
+            String expectedString = ExceptionMessage.INVALID_MEMBER_NAME.getMessage();
+            assertEquals(expectedString, e.getMessage());
+        }
+    }
+}