diff --git a/pallas-applying/src/alonzo.rs b/pallas-applying/src/alonzo.rs
index aac55ff..109d934 100644
--- a/pallas-applying/src/alonzo.rs
+++ b/pallas-applying/src/alonzo.rs
@@ -36,16 +36,16 @@ pub fn validate_alonzo_tx(
     network_id: &u8,
 ) -> ValidationResult {
     let tx_body: &TransactionBody = &mtx.transaction_body;
-    let size: &u32 = &get_alonzo_comp_tx_size(tx_body).ok_or(Alonzo(UnknownTxSize))?;
+    let size: u32 = get_alonzo_comp_tx_size(mtx);
     check_ins_not_empty(tx_body)?;
     check_ins_and_collateral_in_utxos(tx_body, utxos)?;
     check_tx_validity_interval(tx_body, mtx, block_slot)?;
-    check_fee(tx_body, size, mtx, utxos, prot_pps)?;
+    check_fee(tx_body, &size, mtx, utxos, prot_pps)?;
     check_preservation_of_value(tx_body, utxos)?;
     check_min_lovelace(tx_body, prot_pps)?;
     check_output_val_size(tx_body, prot_pps)?;
     check_network_id(tx_body, network_id)?;
-    check_tx_size(size, prot_pps)?;
+    check_tx_size(&size, prot_pps)?;
     check_tx_ex_units(mtx, prot_pps)?;
     check_witness_set(mtx, utxos)?;
     check_languages(mtx, prot_pps)?;
diff --git a/pallas-applying/src/babbage.rs b/pallas-applying/src/babbage.rs
index a060451..ea4b11b 100644
--- a/pallas-applying/src/babbage.rs
+++ b/pallas-applying/src/babbage.rs
@@ -38,16 +38,16 @@ pub fn validate_babbage_tx(
     network_id: &u8,
 ) -> ValidationResult {
     let tx_body: &MintedTransactionBody = &mtx.transaction_body.clone();
-    let size: &u32 = &get_babbage_tx_size(tx_body).ok_or(Babbage(UnknownTxSize))?;
+    let size: u32 = get_babbage_tx_size(mtx).ok_or(Babbage(UnknownTxSize))?;
     check_ins_not_empty(tx_body)?;
     check_all_ins_in_utxos(tx_body, utxos)?;
     check_tx_validity_interval(tx_body, block_slot)?;
-    check_fee(tx_body, size, mtx, utxos, prot_pps)?;
+    check_fee(tx_body, &size, mtx, utxos, prot_pps)?;
     check_preservation_of_value(tx_body, utxos)?;
     check_min_lovelace(tx_body, prot_pps)?;
     check_output_val_size(tx_body, prot_pps)?;
     check_network_id(tx_body, network_id)?;
-    check_tx_size(size, prot_pps)?;
+    check_tx_size(&size, prot_pps)?;
     check_tx_ex_units(mtx, prot_pps)?;
     check_minting(tx_body, mtx)?;
     check_well_formedness(tx_body, mtx)?;
diff --git a/pallas-applying/src/byron.rs b/pallas-applying/src/byron.rs
index c95c165..ac413ab 100644
--- a/pallas-applying/src/byron.rs
+++ b/pallas-applying/src/byron.rs
@@ -12,10 +12,7 @@ use crate::utils::{
 use pallas_addresses::byron::{
     AddrAttrs, AddrType, AddressId, AddressPayload, ByronAddress, SpendingData,
 };
-use pallas_codec::{
-    minicbor::{encode, Encoder},
-    utils::CborWrap,
-};
+use pallas_codec::{minicbor::Encoder, utils::CborWrap};
 use pallas_crypto::{
     hash::Hash,
     key::ed25519::{PublicKey, Signature},
@@ -32,13 +29,13 @@ pub fn validate_byron_tx(
     prot_magic: &u32,
 ) -> ValidationResult {
     let tx: &Tx = &mtxp.transaction;
-    let size: &u64 = &get_tx_size(tx)?;
+    let size: u64 = get_tx_size(mtxp);
     check_ins_not_empty(tx)?;
     check_outs_not_empty(tx)?;
     check_ins_in_utxos(tx, utxos)?;
     check_outs_have_lovelace(tx)?;
-    check_fees(tx, size, utxos, prot_pps)?;
-    check_size(size, prot_pps)?;
+    check_fees(tx, &size, utxos, prot_pps)?;
+    check_size(&size, prot_pps)?;
     check_witnesses(mtxp, utxos, prot_magic)
 }
 
@@ -126,12 +123,8 @@ fn check_size(size: &u64, prot_pps: &ByronProtParams) -> ValidationResult {
     Ok(())
 }
 
-fn get_tx_size(tx: &Tx) -> Result<u64, ValidationError> {
-    let mut buff: Vec<u8> = Vec::new();
-    match encode(tx, &mut buff) {
-        Ok(()) => Ok(buff.len() as u64),
-        Err(_) => Err(Byron(UnknownTxSize)),
-    }
+fn get_tx_size(mtxp: &MintedTxPayload) -> u64 {
+    (mtxp.transaction.raw_cbor().len() + mtxp.witness.raw_cbor().len()) as u64
 }
 
 pub enum TaggedSignature<'a> {
diff --git a/pallas-applying/src/shelley_ma.rs b/pallas-applying/src/shelley_ma.rs
index 5c28064..dbae94e 100644
--- a/pallas-applying/src/shelley_ma.rs
+++ b/pallas-applying/src/shelley_ma.rs
@@ -31,14 +31,14 @@ pub fn validate_shelley_ma_tx(
 ) -> ValidationResult {
     let tx_body: &TransactionBody = &mtx.transaction_body;
     let tx_wits: &MintedWitnessSet = &mtx.transaction_witness_set;
-    let size: &u32 = &get_alonzo_comp_tx_size(tx_body).ok_or(ShelleyMA(UnknownTxSize))?;
+    let size: u32 = get_alonzo_comp_tx_size(mtx);
     check_ins_not_empty(tx_body)?;
     check_ins_in_utxos(tx_body, utxos)?;
     check_ttl(tx_body, block_slot)?;
-    check_tx_size(size, prot_pps)?;
+    check_tx_size(&size, prot_pps)?;
     check_min_lovelace(tx_body, prot_pps, era)?;
     check_preservation_of_value(tx_body, utxos, era)?;
-    check_fees(tx_body, size, prot_pps)?;
+    check_fees(tx_body, &size, prot_pps)?;
     check_network_id(tx_body, network_id)?;
     check_metadata(tx_body, mtx)?;
     check_witnesses(tx_body, tx_wits, utxos)?;
diff --git a/pallas-applying/src/utils.rs b/pallas-applying/src/utils.rs
index 5c375af..69390a4 100644
--- a/pallas-applying/src/utils.rs
+++ b/pallas-applying/src/utils.rs
@@ -7,15 +7,15 @@ pub use environment::*;
 use pallas_addresses::{Address, ShelleyAddress, ShelleyPaymentPart};
 use pallas_codec::{
     minicbor::encode,
-    utils::{Bytes, KeepRaw, KeyValuePairs},
+    utils::{Bytes, KeepRaw, KeyValuePairs, Nullable},
 };
 use pallas_crypto::key::ed25519::{PublicKey, Signature};
 use pallas_primitives::{
     alonzo::{
         AssetName, AuxiliaryData, Coin, MintedTx as AlonzoMintedTx, Multiasset, NativeScript,
-        NetworkId, PlutusScript, PolicyId, TransactionBody, VKeyWitness, Value,
+        NetworkId, PlutusScript, PolicyId, VKeyWitness, Value,
     },
-    babbage::{MintedTransactionBody, MintedTx as BabbageMintedTx, PlutusV2Script},
+    babbage::{MintedTx as BabbageMintedTx, PlutusV2Script},
 };
 use pallas_traverse::{MultiEraInput, MultiEraOutput};
 use std::collections::HashMap;
@@ -24,17 +24,23 @@ pub use validation::*;
 
 pub type UTxOs<'b> = HashMap<MultiEraInput<'b>, MultiEraOutput<'b>>;
 
-pub fn get_alonzo_comp_tx_size(tx_body: &TransactionBody) -> Option<u32> {
-    let mut buff: Vec<u8> = Vec::new();
-    match encode(tx_body, &mut buff) {
-        Ok(()) => Some(buff.len() as u32),
-        Err(_) => None,
+pub fn get_alonzo_comp_tx_size(mtx: &AlonzoMintedTx) -> u32 {
+    match &mtx.auxiliary_data {
+        Nullable::Some(aux_data) => {
+            (aux_data.raw_cbor().len()
+                + mtx.transaction_body.raw_cbor().len()
+                + mtx.transaction_witness_set.raw_cbor().len()) as u32
+        }
+        _ => {
+            (mtx.transaction_body.raw_cbor().len() + mtx.transaction_witness_set.raw_cbor().len())
+                as u32
+        }
     }
 }
 
-pub fn get_babbage_tx_size(tx_body: &MintedTransactionBody) -> Option<u32> {
+pub fn get_babbage_tx_size(mtx: &BabbageMintedTx) -> Option<u32> {
     let mut buff: Vec<u8> = Vec::new();
-    match encode(tx_body, &mut buff) {
+    match encode(mtx, &mut buff) {
         Ok(()) => Some(buff.len() as u32),
         Err(_) => None,
     }