diff --git a/cmd/rpc/admin.go b/cmd/rpc/admin.go
index af9d49e8b6..e84aed9301 100644
--- a/cmd/rpc/admin.go
+++ b/cmd/rpc/admin.go
@@ -297,11 +297,9 @@ func (s *Server) TransactionDAOTransfer(w http.ResponseWriter, r *http.Request,
 func (s *Server) TransactionSubsidy(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
 	// Call the transaction handler with a callback that creates the transaction
 	s.txHandler(w, r, func(p crypto.PrivateKeyI, ptr *txRequest) (lib.TransactionI, error) {
-		// Create a default chainid of 0
-		chainId := uint64(0)
-		// Convert comma separated string of committees to uint64
-		if c, err := stringToCommittees(ptr.Committees); err == nil {
-			chainId = c[0]
+		chainId, err := singleCommitteeID(ptr.Committees)
+		if err != nil {
+			return nil, err
 		}
 		// Retrieve the fee required for this type of transaction
 		if err := s.getFeeFromState(ptr, fsm.MessageSubsidyName); err != nil {
@@ -316,11 +314,9 @@ func (s *Server) TransactionSubsidy(w http.ResponseWriter, r *http.Request, _ ht
 func (s *Server) TransactionCreateOrder(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
 	// Call the transaction handler with a callback that creates the transaction
 	s.txHandler(w, r, func(p crypto.PrivateKeyI, ptr *txRequest) (lib.TransactionI, error) {
-		// Create a default chainid of 0
-		chainId := uint64(0)
-		// Convert comma separated string of committees to uint64
-		if c, err := stringToCommittees(ptr.Committees); err == nil {
-			chainId = c[0]
+		chainId, err := singleCommitteeID(ptr.Committees)
+		if err != nil {
+			return nil, err
 		}
 		// Retrieve the fee required for this type of transaction
 		if err := s.getFeeFromState(ptr, fsm.MessageCreateOrderName); err != nil {
@@ -335,11 +331,9 @@ func (s *Server) TransactionCreateOrder(w http.ResponseWriter, r *http.Request,
 func (s *Server) TransactionEditOrder(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
 	// Call the transaction handler with a callback that creates the transaction
 	s.txHandler(w, r, func(p crypto.PrivateKeyI, ptr *txRequest) (lib.TransactionI, error) {
-		// Create a default chainid of 0
-		chainId := uint64(0)
-		// Convert comma separated string of committees to uint64
-		if c, err := stringToCommittees(ptr.Committees); err == nil {
-			chainId = c[0]
+		chainId, err := singleCommitteeID(ptr.Committees)
+		if err != nil {
+			return nil, err
 		}
 		if err := s.getFeeFromState(ptr, fsm.MessageEditOrderName); err != nil {
 			return nil, err
@@ -353,11 +347,9 @@ func (s *Server) TransactionEditOrder(w http.ResponseWriter, r *http.Request, _
 func (s *Server) TransactionDeleteOrder(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
 	// Call the transaction handler with a callback that creates the transaction
 	s.txHandler(w, r, func(p crypto.PrivateKeyI, ptr *txRequest) (lib.TransactionI, error) {
-		// Create a default chainid of 0
-		chainId := uint64(0)
-		// Convert comma separated string of committees to uint64
-		if c, err := stringToCommittees(ptr.Committees); err == nil {
-			chainId = c[0]
+		chainId, err := singleCommitteeID(ptr.Committees)
+		if err != nil {
+			return nil, err
 		}
 		// Retrieve the fee required for this type of transaction
 		if err := s.getFeeFromState(ptr, fsm.MessageDeleteOrderName); err != nil {
@@ -372,11 +364,9 @@ func (s *Server) TransactionDeleteOrder(w http.ResponseWriter, r *http.Request,
 func (s *Server) TransactionDexLimitOrder(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
 	// Call the transaction handler with a callback that creates the transaction
 	s.txHandler(w, r, func(p crypto.PrivateKeyI, ptr *txRequest) (lib.TransactionI, error) {
-		// Create a default chainid of 0
-		chainId := uint64(0)
-		// Convert comma separated string of committees to uint64
-		if c, err := stringToCommittees(ptr.Committees); err == nil {
-			chainId = c[0]
+		chainId, err := singleCommitteeID(ptr.Committees)
+		if err != nil {
+			return nil, err
 		}
 		// Retrieve the fee required for this type of transaction
 		if err := s.getFeeFromState(ptr, fsm.MessageDexLimitOrderName); err != nil {
@@ -391,11 +381,9 @@ func (s *Server) TransactionDexLimitOrder(w http.ResponseWriter, r *http.Request
 func (s *Server) TransactionDexLiquidityDeposit(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
 	// Call the transaction handler with a callback that creates the transaction
 	s.txHandler(w, r, func(p crypto.PrivateKeyI, ptr *txRequest) (lib.TransactionI, error) {
-		// Create a default chainid of 0
-		chainId := uint64(0)
-		// Convert comma separated string of committees to uint64
-		if c, err := stringToCommittees(ptr.Committees); err == nil {
-			chainId = c[0]
+		chainId, err := singleCommitteeID(ptr.Committees)
+		if err != nil {
+			return nil, err
 		}
 		// Retrieve the fee required for this type of transaction
 		if err := s.getFeeFromState(ptr, fsm.MessageDexLiquidityDepositName); err != nil {
@@ -410,11 +398,9 @@ func (s *Server) TransactionDexLiquidityDeposit(w http.ResponseWriter, r *http.R
 func (s *Server) TransactionDexLiquidityWithdraw(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
 	// Call the transaction handler with a callback that creates the transaction
 	s.txHandler(w, r, func(p crypto.PrivateKeyI, ptr *txRequest) (lib.TransactionI, error) {
-		// Create a default chainid of 0
-		chainId := uint64(0)
-		// Convert comma separated string of committees to uint64
-		if c, err := stringToCommittees(ptr.Committees); err == nil {
-			chainId = c[0]
+		chainId, err := singleCommitteeID(ptr.Committees)
+		if err != nil {
+			return nil, err
 		}
 		// Retrieve the fee required for this type of transaction
 		if err := s.getFeeFromState(ptr, fsm.MessageDexLiquidityWithdrawName); err != nil {
@@ -822,6 +808,22 @@ func stringToCommittees(s string) (committees []uint64, error error) {
 	return
 }
 
+// singleCommitteeID parses the one chain-scoped committee accepted by order,
+// subsidy, and DEX transaction endpoints.
+func singleCommitteeID(s string) (uint64, error) {
+	if strings.TrimSpace(s) == "" {
+		return 0, nil
+	}
+	committees, err := stringToCommittees(s)
+	if err != nil {
+		return 0, err
+	}
+	if len(committees) != 1 {
+		return 0, fmt.Errorf("expected exactly one committee, got %d", len(committees))
+	}
+	return committees[0], nil
+}
+
 // getAddressFromNickname retrieves the account address for the supplied nickname
 func getAddressFromNickname(ptr *txRequest, keystore *crypto.Keystore) {
 	// Populate Signer field if SignerNickname is present
diff --git a/cmd/rpc/admin_test.go b/cmd/rpc/admin_test.go
new file mode 100644
index 0000000000..d44d0ce9e9
--- /dev/null
+++ b/cmd/rpc/admin_test.go
@@ -0,0 +1,54 @@
+package rpc
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestSingleCommitteeID(t *testing.T) {
+	tests := []struct {
+		name      string
+		input     string
+		want      uint64
+		wantError string
+	}{
+		{
+			name:  "empty defaults to root chain",
+			input: "",
+			want:  0,
+		},
+		{
+			name:  "blank defaults to root chain",
+			input: "   ",
+			want:  0,
+		},
+		{
+			name:  "single committee",
+			input: "12",
+			want:  12,
+		},
+		{
+			name:      "malformed committee",
+			input:     "nested-12",
+			wantError: "invalid syntax",
+		},
+		{
+			name:      "multiple committees rejected",
+			input:     "1,2",
+			wantError: "expected exactly one committee",
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			got, err := singleCommitteeID(test.input)
+			if test.wantError != "" {
+				require.ErrorContains(t, err, test.wantError)
+				return
+			}
+			require.NoError(t, err)
+			require.Equal(t, test.want, got)
+		})
+	}
+}