diff --git a/codegen/src/api/extrinsic.rs b/codegen/src/api/extrinsic.rs
new file mode 100644
index 0000000000..a9d3e55a5f
--- /dev/null
+++ b/codegen/src/api/extrinsic.rs
@@ -0,0 +1,79 @@
+// Copyright 2019-2021 Parity Technologies (UK) Ltd.
+// This file is part of subxt.
+//
+// subxt is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// subxt is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with subxt.  If not, see <http://www.gnu.org/licenses/>.
+
+use crate::types::TypeGenerator;
+use frame_metadata::ExtrinsicMetadata;
+use heck::SnakeCase as _;
+use proc_macro2::TokenStream as TokenStream2;
+use proc_macro_error::abort_call_site;
+use quote::{
+    format_ident,
+    quote,
+};
+use scale_info::form::PortableForm;
+
+pub fn generate_extensions(
+    type_gen: &TypeGenerator,
+    extrinsic_metadata: &ExtrinsicMetadata<PortableForm>,
+    types_mod_ident: &syn::Ident,
+) -> TokenStream2 {
+
+    let extensions = extrinsic_metadata
+        .signed_extensions
+        .iter()
+        .map(|ext| {
+            let id = &ext.identifier;
+            let type_ident = format_ident!("{}", id);
+            let extra_ty = type_gen.resolve_type_path(ext.ty.id(), &[]);
+            let additional_signed_ty = type_gen.resolve_type_path(ext.additional_signed.id(), &[]);
+            quote! {
+                pub struct #type_ident {
+                    pub extra: #extra_ty,
+                    pub additional_signed: #additional_signed_ty,
+                }
+
+                // impl #type_ident {
+                //     pub fn new(extra: #, additional_signed) -> Self {
+                //
+                //     }
+                // }
+
+                // todo: implement constructor for extra and additional signed data,
+                // todo: possibly for use via a builder
+
+                impl ::subxt::sp_runtime::traits::SignedExtension for #type_ident {
+                    const IDENTIFIER: &'static str = #id;
+                    type AccountId = ();
+                    type Call = ();
+                    type AdditionalSigned = #additional_signed_ty;
+                    type Pre = ();
+                    fn additional_signed(
+                        &self,
+                    ) -> Result<Self::AdditionalSigned, TransactionValidityError> {
+                        Ok(self.additional_signed)
+                    }
+                }
+            }
+        });
+
+    quote! {
+        pub mod extensions {
+            use super::#types_mod_ident;
+
+
+        }
+    }
+}
\ No newline at end of file
diff --git a/codegen/src/api/mod.rs b/codegen/src/api/mod.rs
index bc46d02745..b5cdef69bf 100644
--- a/codegen/src/api/mod.rs
+++ b/codegen/src/api/mod.rs
@@ -16,6 +16,7 @@
 
 mod calls;
 mod events;
+mod extrinsic;
 mod storage;
 
 use super::GeneratedTypeDerives;
@@ -201,6 +202,8 @@ impl RuntimeGenerator {
             }
         };
 
+        let extensions = extrinsic::generate_extensions(&type_gen, &self.metadata.extrinsic, types_mod_ident);
+
         let mod_ident = item_mod_ir.ident;
         let pallets_with_storage =
             pallets_with_mod_names