diff --git a/blockchain/transaction.go b/blockchain/transaction.go
index b813868..c3977d5 100644
--- a/blockchain/transaction.go
+++ b/blockchain/transaction.go
@@ -105,5 +105,5 @@ func (t *Transaction) InputsEqualOutputs(other ...*Transaction) bool {
 		outAmount += output.Amount
 	}
 
-	return (int(outAmount) - int(inAmount)) != 0
+	return (int(outAmount) - int(inAmount)) == 0
 }
diff --git a/blockchain/validation.go b/blockchain/validation.go
index 8668949..f7db8d2 100644
--- a/blockchain/validation.go
+++ b/blockchain/validation.go
@@ -49,7 +49,7 @@ func (bc *BlockChain) ValidTransaction(t *Transaction) (bool, TransactionCode) {
 	}
 
 	// Check that output to sender in input is equal to outputs in t
-	if input.InputsEqualOutputs(t) {
+	if !input.InputsEqualOutputs(t) {
 		return false, Overspend
 	}
 
@@ -94,7 +94,7 @@ func (bc *BlockChain) ValidBlock(b *Block) (bool, BlockCode) {
 		for j, trB := range b.Transactions {
 			if (i != j) && (trA.Input.Hash == trB.Input.Hash) {
 				inputTr := bc.GetInputTransaction(trA)
-				if inputTr.InputsEqualOutputs(trA, trB) {
+				if !inputTr.InputsEqualOutputs(trA, trB) {
 					return false, DoubleSpend
 				}
 			}