diff --git a/pkg/api/controllers/transaction_controller.go b/pkg/api/controllers/transaction_controller.go
index 50a3c84b6..7b6347062 100644
--- a/pkg/api/controllers/transaction_controller.go
+++ b/pkg/api/controllers/transaction_controller.go
@@ -80,14 +80,16 @@ func (ctl *TransactionController) PostTransaction(c *gin.Context) {
 			switch eerr.Code {
 			case storage.ConstraintFailed:
 				ctl.responseError(c, http.StatusConflict, err)
-				return
+			default:
+				ctl.responseError(c, http.StatusInternalServerError, err)
 			}
+		case *ledger.InsufficientFundError:
+			ctl.responseError(c, http.StatusBadRequest, err)
+		case *ledger.ValidationError:
+			ctl.responseError(c, http.StatusBadRequest, err)
+		default:
+			ctl.responseError(c, http.StatusInternalServerError, err)
 		}
-		ctl.responseError(
-			c,
-			http.StatusInternalServerError,
-			err,
-		)
 		return
 	}
 	ctl.response(
@@ -150,11 +152,21 @@ func (ctl *TransactionController) RevertTransaction(c *gin.Context) {
 	l, _ := c.Get("ledger")
 	err := l.(*ledger.Ledger).RevertTransaction(c.Request.Context(), c.Param("txid"))
 	if err != nil {
-		ctl.responseError(
-			c,
-			http.StatusInternalServerError,
-			err,
-		)
+		switch eerr := err.(type) {
+		case *storage.Error:
+			switch eerr.Code {
+			case storage.ConstraintFailed:
+				ctl.responseError(c, http.StatusConflict, err)
+			default:
+				ctl.responseError(c, http.StatusInternalServerError, err)
+			}
+		case *ledger.InsufficientFundError:
+			ctl.responseError(c, http.StatusBadRequest, err)
+		case *ledger.ValidationError:
+			ctl.responseError(c, http.StatusBadRequest, err)
+		default:
+			ctl.responseError(c, http.StatusInternalServerError, err)
+		}
 		return
 	}
 	ctl.response(
diff --git a/pkg/ledger/error.go b/pkg/ledger/error.go
new file mode 100644
index 000000000..54f436bb8
--- /dev/null
+++ b/pkg/ledger/error.go
@@ -0,0 +1,29 @@
+package ledger
+
+import "fmt"
+
+type InsufficientFundError struct {
+	Asset string
+}
+
+func (e InsufficientFundError) Error() string {
+	return fmt.Sprintf("balance.insufficient.%s", e.Asset)
+}
+
+func NewInsufficientFundError(asset string) *InsufficientFundError {
+	return &InsufficientFundError{Asset: asset}
+}
+
+type ValidationError struct {
+	Msg string
+}
+
+func (v ValidationError) Error() string {
+	return v.Msg
+}
+
+func NewValidationError(msg string) *ValidationError {
+	return &ValidationError{
+		Msg: msg,
+	}
+}
\ No newline at end of file
diff --git a/pkg/ledger/ledger.go b/pkg/ledger/ledger.go
index 92334701b..c207cfc10 100644
--- a/pkg/ledger/ledger.go
+++ b/pkg/ledger/ledger.go
@@ -57,7 +57,7 @@ func (l *Ledger) Commit(ctx context.Context, ts []core.Transaction) ([]core.Tran
 	for i := range ts {
 
 		if len(ts[i].Postings) == 0 {
-			return ts, errors.New("transaction has no postings")
+			return ts, NewValidationError("transaction has no postings")
 		}
 
 		ts[i].ID = count + int64(i)
@@ -67,6 +67,9 @@ func (l *Ledger) Commit(ctx context.Context, ts []core.Transaction) ([]core.Tran
 		last = &ts[i]
 
 		for _, p := range ts[i].Postings {
+			if p.Amount < 0 {
+				return ts, NewValidationError("negative amount")
+			}
 			if _, ok := rf[p.Source]; !ok {
 				rf[p.Source] = map[string]int64{}
 			}
@@ -101,7 +104,6 @@ func (l *Ledger) Commit(ctx context.Context, ts []core.Transaction) ([]core.Tran
 		}
 
 		balances, err := l.store.AggregateBalances(ctx, addr)
-
 		if err != nil {
 			return ts, err
 		}
@@ -110,10 +112,7 @@ func (l *Ledger) Commit(ctx context.Context, ts []core.Transaction) ([]core.Tran
 			balance, ok := balances[asset]
 
 			if !ok || balance < checks[asset] {
-				return ts, fmt.Errorf(
-					"balance.insufficient.%s",
-					asset,
-				)
+				return ts, NewInsufficientFundError(asset)
 			}
 		}
 	}
@@ -228,13 +227,13 @@ func (l *Ledger) SaveMeta(ctx context.Context, targetType string, targetID strin
 	defer unlock()
 
 	if targetType == "" {
-		return errors.New("empty target type")
+		return NewValidationError("empty target type")
 	}
 	if targetType != targetTypeTransaction && targetType != targetTypeAccount {
-		return fmt.Errorf("unknown target type '%s'", targetType)
+		return NewValidationError(fmt.Sprintf("unknown target type '%s'", targetType))
 	}
 	if targetID == "" {
-		return errors.New("empty target id")
+		return NewValidationError("empty target id")
 	}
 
 	lastMetaID, err := l.store.LastMetaID(ctx)