diff --git a/src/block_ops.dats b/src/block_ops.dats
index c002b54..bbe8e9a 100644
--- a/src/block_ops.dats
+++ b/src/block_ops.dats
@@ -17,7 +17,8 @@ file_write_block(e: block): void
 implement
 mine(hd) = let 
   val (ind, nonce, trns, code, h) = hd
-  val theValids = list0_filter(trns, lam(t) => is_valid_transact(t))
+  val temp = list0_filter(trns, lam(t) => is_valid_transact(t))
+  val theValids = list0_filter(temp, lam(t) => make_transact(t))
   
   fun aux(hd: header): block = let
       val currh = sha256(encode_header(hd))
diff --git a/src/cli.dats b/src/cli.dats
index 5108bc6..2b53795 100644
--- a/src/cli.dats
+++ b/src/cli.dats
@@ -121,6 +121,7 @@ case+ args of
     then let val coins = get_coins(a) in println!("Balance of ", a, " is ", coins) end
     else println!("unrecognized miner")
 
+
 implement
 do_execute(args) =
 case+ args of 
@@ -138,6 +139,7 @@ in
   file_write_contract((f, val2str(interp(parse_lisp(f)))))
 end
 
+
 implement
 do_transact(args) = 
 case+ args of
@@ -152,15 +154,23 @@ case+ args of
         let val trns = (a, b, string2int(c)) 
         in transact(trns) end
 
+
 implement
 do_mine(args) = 
 case+ args of
 | nil0() => (println!("must provide <miner> argument"); ())
 | cons0(a, _) => let
-  val test = is_miner(a)
+  val test_miner = is_miner(a)
+  val test_transact = list0_length(list0_filter(get_data(), lam(t) => is_valid_transact(t))) > 0
+  val test_code = list0_length(get_result()) > 0
+  val test = test_miner andalso test_transact andalso test_code
 in
-  if test then (chain_add(); reward(a); clear_transact())
-  else (println!("unrecognized miner - please define miner first"); ())
+  ifcase
+  | test => (chain_add(); reward(a); clear_transact())
+  | ~test_miner => (println!("unrecognized miner - please define miner first"); ())
+  | ~test_transact => (println!("must have at least one valid transaction per block"); ())
+  | ~test_code => (println!("must have at least one smart contract per block"); ())
+  | _ => (println!("True = False?"); ())
 end
 
 
diff --git a/src/trans_ops.dats b/src/trans_ops.dats
index b865b6c..feca989 100644
--- a/src/trans_ops.dats
+++ b/src/trans_ops.dats
@@ -12,6 +12,10 @@ extern
 fun
 is_valid_transact(t: transaction): bool
 
+extern
+fun
+make_transact(t: transaction): bool //same as is_valid_transact with necessary side effect
+
 extern
 fun
 get_data(): data
@@ -142,6 +146,30 @@ is_valid_transact(t) = let
   val receiver = t.1
   val amount = t.2
   val test_exists = is_miner(sender) andalso is_miner(receiver)
+in
+  if test_exists
+  then
+  ( 
+    let 
+      val sender_balance = get_coins(sender)
+      val receiver_balance = get_coins(receiver)
+      val test_balance = sender_balance >= amount
+    in
+      if test_balance
+      then true
+      else false
+    end
+  )
+  else false
+end
+
+
+implement
+make_transact(t) = let
+  val sender = t.0
+  val receiver = t.1
+  val amount = t.2
+  val test_exists = is_miner(sender) andalso is_miner(receiver)
 in
   if test_exists
   then
@@ -170,6 +198,7 @@ get_data() = let
   val ft = fileref_open_opt("./transaction.txt", file_mode_r)
 in
   case- ft of
+  | ~None_vt() => nil0()
   | ~Some_vt(trns) => let
       val theLines = streamize_fileref_line(trns)
     in