diff --git a/goodchain/src/helpers/BlockHelper.py b/goodchain/src/helpers/BlockHelper.py
index 920d4ca..1b25188 100644
--- a/goodchain/src/helpers/BlockHelper.py
+++ b/goodchain/src/helpers/BlockHelper.py
@@ -65,7 +65,7 @@ def exploreBlocks(self):
             utilityHelper.clearScreen()
             return
         case "1":
-            print("Validating block... TODO")
+            blocks[user_input].is_valid()
         case "2":
             utilityHelper.clearScreen()
             x = 0
@@ -185,10 +185,16 @@ def createBlock(self):
 
     # create block
     for i in selected_transactions:
-        # if not transaction[i].is_valid():
-        #     # Return transaction as 'invalid' transaction
-        #     # stop mining with the error "Invalid transaction found. transaction removed from pool. Please restart mining a block..."
-        #     pass
+        if not transactions[i].is_valid():
+            self.db.createLog(transactions[i].inputs[0][0], time.time(), f"Transaction of {transactions[i].outputs[0][1]} with {transactions[i].inputs[0][1] - transactions[i].outputs[0][1]} coins fee is declined")
+            try:
+                del transactions[i]
+            except:
+                return False
+            for transaction in transactions:
+                utilityHelper.addFile("../data/transaction_pool.dat", transaction)
+            print(f"{utilityHelper.errorMessage('ERROR! Invalid transaction found. transaction removed from pool. Please restart mining a block...')}")
+            return False
         block.addTx(transactions[i])
 
     
@@ -229,12 +235,12 @@ def createBlock(self):
     block.date = time.time()
     block.blockHash = block.computeHash()
 
-    utilityHelper.saveFile("../data/ledger.dat", block)
+    utilityHelper.addFile("../data/ledger.dat", block)
     utilityHelper.resetFile("../data/transaction_pool.dat")
     transaction_count = 0
     for transaction in transactions:
         if transaction_count not in selected_transactions:
-            utilityHelper.saveFile("../data/transaction_pool.dat", transaction)
+            utilityHelper.addFile("../data/transaction_pool.dat", transaction)
         transaction_count += 1
 
     return True
@@ -275,7 +281,7 @@ def validateMinedBlock(self):
             new_reward = Tx()
             new_reward.createRewardTransaction(self.user.public_ser, self.user.private_ser, "MINE", fees)
             self.db.createLog(new_block.metadata['miner'], time.time(), f"Block id {new_block.id}, is validated!")
-            utilityHelper.saveFile("../data/transaction_pool.dat", new_reward)
+            utilityHelper.addFile("../data/transaction_pool.dat", new_reward)
 
 
         try:
@@ -286,7 +292,7 @@ def validateMinedBlock(self):
         utilityHelper.resetFile("../data/ledger.dat")
         blocks.append(new_block)
         for block in blocks:
-            utilityHelper.saveFile("../data/ledger.dat", block)
+            utilityHelper.addFile("../data/ledger.dat", block)
         
         return True
     
@@ -295,9 +301,9 @@ def validateMinedBlock(self):
         if new_block.metadata['false_validations'] >= 3:
             # Create log for miner
             self.db.createLog(new_block.metadata['miner'], time.time(), f"Block id {new_block.id}, was flagged invalid. Mine unsuccesful...")
-            # set transactions in block back to the pool
+            # setsaveFil transactions in block back to the pool
             for transaction in new_block.data:
-                utilityHelper.saveFile("../data/transaction_pool.dat", transaction)
+                utilityHelper.addFile("../data/transaction_pool.dat", transaction)
             try:
                 del blocks[-1]
             except:
@@ -306,7 +312,7 @@ def validateMinedBlock(self):
             
         utilityHelper.resetFile("../data/ledger.dat")
         for block in blocks:
-            utilityHelper.saveFile("../data/ledger.dat", block)
+            utilityHelper.addFile("../data/ledger.dat", block)
 
         return True