diff --git a/src/main.rs b/src/main.rs
index a62b0cc..545e25b 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -21,8 +21,8 @@ enum Command {
     Sign {
         /// Signing key (hex encoded)
         skey: String,
-        /// Subbit id (hex encoded)
-        id: String,
+        /// Tag (hex encoded)
+        tag: String,
         /// Amount (unsigned integer u64. Seems to be largest permitted)
         amt: u64,
     },
@@ -30,8 +30,8 @@ enum Command {
     Verify {
         /// Verifying key (hex encoded)
         vkey: String,
-        /// Subbit id (hex encoded)
-        id: String,
+        /// Tag (hex encoded)
+        tag: String,
         /// Amount (unsigned integer u64. Seems to be largest permitted)
         amt: u64,
         /// Signature (hex encoded)
@@ -49,17 +49,22 @@ fn main() -> anyhow::Result<()> {
             let skey = skey_from_seed(seed)?;
             println!("{}", serde_json::to_string(&KeyPairHex::from_skey(&skey))?);
         }
-        Some(Command::Sign { skey, id, amt }) => {
+        Some(Command::Sign { skey, tag, amt }) => {
             let skey = skey_from_hex(&skey)?;
-            let iou = Iou::from_cli(id, amt)?;
+            let iou = Iou::from_cli(tag, amt)?;
             let msg = iou.to_vec()?;
             let sig = sign(&mut skey.clone(), msg.clone());
             let _ver = verify(&skey.verifying_key(), &msg, &sig);
             println!("{}", sig_to_hex(&sig));
         }
-        Some(Command::Verify { vkey, id, amt, sig }) => {
+        Some(Command::Verify {
+            vkey,
+            tag,
+            amt,
+            sig,
+        }) => {
             let vkey = vkey_from_hex(&vkey)?;
-            let iou = Iou::from_cli(id, amt)?;
+            let iou = Iou::from_cli(tag, amt)?;
             let msg = iou.to_vec()?;
             let sig = sig_from_hex(&sig)?;
             let res = verify(&vkey, &msg, &sig)?;
@@ -176,21 +181,21 @@ impl KeyPairHex {
     }
 }
 
-pub fn id_from_hex(s: &str) -> Result<Vec<u8>, anyhow::Error> {
-    let id = hex::decode(s)?;
-    Ok(id)
+pub fn tag_from_hex(s: &str) -> Result<Vec<u8>, anyhow::Error> {
+    let tag = hex::decode(s)?;
+    Ok(tag)
 }
 
 #[derive(Serialize, Deserialize)]
 struct Iou {
-    subbit_id: Vec<u8>,
+    tag: Vec<u8>,
     amount: u64,
 }
 
 impl Iou {
-    fn from_cli(id: String, amt: u64) -> Result<Self, anyhow::Error> {
+    fn from_cli(tag: String, amt: u64) -> Result<Self, anyhow::Error> {
         Ok(Self {
-            subbit_id: id_from_hex(&id)?,
+            tag: tag_from_hex(&tag)?,
             amount: amt,
         })
     }
@@ -200,9 +205,7 @@ impl Iou {
             tag: 121,
             any_constructor: None,
             fields: pallas_primitives::MaybeIndefArray::Indef(vec![
-                PlutusData::BoundedBytes(pallas_primitives::BoundedBytes::from(
-                    self.subbit_id.clone(),
-                )),
+                PlutusData::BoundedBytes(pallas_primitives::BoundedBytes::from(self.tag.clone())),
                 PlutusData::BigInt(pallas_primitives::BigInt::Int(
                     pallas_primitives::Int::try_from(self.amount as i128)?,
                 )),
@@ -218,16 +221,16 @@ impl Iou {
 
     fn gen(seed: Option<u64>) -> Self {
         let mut rng: rand_chacha::ChaCha8Rng = SeedableRng::seed_from_u64(seed.unwrap_or(0));
-        let subbit_id: Vec<u8> = rng.next_u64().to_le_bytes().into();
+        let tag: Vec<u8> = rng.next_u64().to_le_bytes().into();
         let amount = rng.next_u64();
-        Iou { subbit_id, amount }
+        Iou { tag, amount }
     }
 }
 
 #[derive(Serialize, Deserialize)]
 struct SignedIou {
     vkey: String,
-    subbit_id: String,
+    tag: String,
     amount: u64,
     msg: String,
     sig: String,
@@ -242,7 +245,7 @@ impl SignedIou {
         let sig = sign(&mut skey.clone(), msg.clone());
         Ok(Self {
             vkey: vkey_to_hex(&vkey),
-            subbit_id: hex::encode(iou.subbit_id),
+            tag: hex::encode(iou.tag),
             amount: iou.amount,
             msg: hex::encode(&msg),
             sig: sig_to_hex(&sig),
@@ -252,14 +255,14 @@ impl SignedIou {
     fn aiken_fmt(self: Self, seed: Option<u64>) {
         let Self {
             vkey,
-            subbit_id,
+            tag,
             amount,
             msg,
             sig,
         } = self;
         println!("const i{} = IouTest {{", seed.unwrap_or(0),);
         println!("  vkey: {}", aiken_hex(&vkey));
-        println!("  subbit_id: {}", aiken_hex(&subbit_id));
+        println!("  tag: {}", aiken_hex(&tag));
         println!("  amount: {},", amount);
         println!("  msg: {}", aiken_hex(&msg));
         println!("  sig: {}", aiken_hex(&sig));
@@ -270,7 +273,7 @@ impl SignedIou {
 fn aiken_test(seed: Option<u64>) {
     println!("test test_i{} () {{", seed.unwrap_or(0));
     println!("  let i = i{}", seed.unwrap_or(0));
-    println!("  verify_iou(i.vkey, i.subbit_id, t.Iou (i.amount, i.sig))");
+    println!("  verify_iou(i.vkey, i.tag, t.Iou (i.amount, i.sig))");
     println!("}}");
 }
 
diff --git a/test.ak b/test.ak
index 4b86db2..261ed65 100644
--- a/test.ak
+++ b/test.ak
@@ -1,7 +1,7 @@
 
 const i0 = IouTest {
   vkey: #"3b6a27bcceb6a42d62a3a8d02a6f0d73653215771de243a63ac048a18b59da29",
-  subbit_id: #"6c3b9aa767f785b5",
+  tag: #"6c3b9aa767f785b5",
   amount: 8594738769458413623,
   msg: #"d8799f486c3b9aa767f785b51b7746a55fbad8c037ff",
   sig: #"8bb7cb5fc82b23fac9114e9a4913f3b01c4db608e6189f01eeb431c7cd0c8c6e28484cdcc25aa895a715622598110754ede40f390797179a70e373856450ce03"
@@ -9,13 +9,13 @@ const i0 = IouTest {
 
 test test_i0 () {
   let i = i0
-  verify_iou(i.vkey, i.subbit_id, t.Iou (i.amount, i.sig))
+  verify_iou(i.vkey, i.tag, t.Iou (i.amount, i.sig))
 }
 
 
 const i1 = IouTest {
   vkey: #"cecc1507dc1ddd7295951c290888f095adb9044d1b73d696e6df065d683bd4fc",
-  subbit_id: #"b10da48cea4c0967",
+  tag: #"b10da48cea4c0967",
   amount: 1482817706323250795,
   msg: #"d8799f48b10da48cea4c09671b149406d8fc0e8e6bff",
   sig: #"7f96d963c32e225ae0a1fe1491466f277cd4cde77cd4f8335578fd888b61942af64972e02efc3a603241f2d84bb5df95b18f57e2f88e4d63c249716b068d8d01"
@@ -23,13 +23,13 @@ const i1 = IouTest {
 
 test test_i1 () {
   let i = i1
-  verify_iou(i.vkey, i.subbit_id, t.Iou (i.amount, i.sig))
+  verify_iou(i.vkey, i.tag, t.Iou (i.amount, i.sig))
 }
 
 
 const i2 = IouTest {
   vkey: #"6b79c57e6a095239282c04818e96112f3f03a4001ba97a564c23852a3f1ea5fc",
-  subbit_id: #"c51b8a31c98b9fe1",
+  tag: #"c51b8a31c98b9fe1",
   amount: 10116765682372994352,
   msg: #"d8799f48c51b8a31c98b9fe11b8c65f8c985b46530ff",
   sig: #"7e6161aab7aff7d73afe83b176d0f3549dc81a5c69ff35aaa7576417e69d7eb81b070d8aa4ae115a6beff99851be1b6266b66d4b2a3d56b4ae499bbc66d8f306"
@@ -37,13 +37,13 @@ const i2 = IouTest {
 
 test test_i2 () {
   let i = i2
-  verify_iou(i.vkey, i.subbit_id, t.Iou (i.amount, i.sig))
+  verify_iou(i.vkey, i.tag, t.Iou (i.amount, i.sig))
 }
 
 
 const i3 = IouTest {
   vkey: #"dadbd184a2d526f1ebdd5c06fdad9359b228759b4d7f79d66689fa254aad8546",
-  subbit_id: #"5de9bc1bb4cb7a9f",
+  tag: #"5de9bc1bb4cb7a9f",
   amount: 1499751601245649308,
   msg: #"d8799f485de9bc1bb4cb7a9f1b14d03022a391f99cff",
   sig: #"c6ca9a4e75691b030d416bb8316d4cf43601b8764d88f8cdbd36207136334abbd819cd00ac77962f7a8dbc494d253f147b5c9d78bf3a77fb6435d0f318d32d09"
@@ -51,13 +51,13 @@ const i3 = IouTest {
 
 test test_i3 () {
   let i = i3
-  verify_iou(i.vkey, i.subbit_id, t.Iou (i.amount, i.sig))
+  verify_iou(i.vkey, i.tag, t.Iou (i.amount, i.sig))
 }
 
 
 const i4 = IouTest {
   vkey: #"9be3287795907809407e14439ff198d5bfc7dce6f9bc743cb369146f610b4801",
-  subbit_id: #"22cfaefc92e4edb9",
+  tag: #"22cfaefc92e4edb9",
   amount: 1287912097577021104,
   msg: #"d8799f4822cfaefc92e4edb91b11df953aa601aeb0ff",
   sig: #"8775af7f57f681bddb8ad3682f662dcfd0fbb09b0a0fe652d880fc3d96f60f66225f4d5bc31e7a1acb729ffebec5ed0666b93e4acbc26392103a1e7878638f0e"
@@ -65,6 +65,6 @@ const i4 = IouTest {
 
 test test_i4 () {
   let i = i4
-  verify_iou(i.vkey, i.subbit_id, t.Iou (i.amount, i.sig))
+  verify_iou(i.vkey, i.tag, t.Iou (i.amount, i.sig))
 }