diff --git a/src/firefly.rs b/src/firefly.rs
index 34f7c1c..4d1add7 100644
--- a/src/firefly.rs
+++ b/src/firefly.rs
@@ -1,6 +1,7 @@
 use reqwest::header::{HeaderMap, HeaderValue};
 use reqwest::Client;
-use serde::Deserialize;
+use serde::{Deserialize, Serialize};
+use tracing::{error, info};
 
 pub struct Firefly {
     url: String,
@@ -9,9 +10,11 @@ pub struct Firefly {
 
 #[derive(Deserialize)]
 pub struct TransactionSplit {
+    pub transaction_journal_id: String,
     pub date: chrono::DateTime<chrono::FixedOffset>,
     pub amount: String,
     pub description: String,
+    pub notes: Option<String>,
 }
 
 #[derive(Deserialize)]
@@ -36,6 +39,57 @@ pub struct TransactionSingle {
     pub data: TransactionRead,
 }
 
+#[derive(Serialize)]
+pub struct TransactionSplitUpdate {
+    pub transaction_journal_id: String,
+    pub amount: String,
+    pub notes: Option<String>,
+}
+
+#[derive(Serialize)]
+pub struct TransactionUpdate {
+    pub transactions: Vec<TransactionSplitUpdate>,
+}
+
+#[derive(Serialize)]
+#[non_exhaustive]
+enum AttachableType {
+    TransactionJournal,
+}
+
+#[derive(Serialize)]
+struct AttachmentStore {
+    filename: String,
+    attachable_type: AttachableType,
+    attachable_id: String,
+}
+
+#[derive(Deserialize)]
+struct AttachmentRead {
+    id: String,
+}
+
+#[derive(Deserialize)]
+struct AttachmentSingle {
+    data: AttachmentRead,
+}
+
+impl TransactionRead {
+    pub fn amount(&self) -> f64 {
+        self.attributes
+            .transactions
+            .iter()
+            .filter_map(|t| match t.amount.parse::<f64>() {
+                Ok(v) => Some(v),
+                Err(e) => {
+                    error!("Invalid amount: {}", e);
+                    None
+                },
+            })
+            .sum()
+    }
+}
+
 impl Firefly {
     pub fn new(url: impl Into<String>, token: &str) -> Self {
         let mut headers = HeaderMap::new();
@@ -83,4 +137,49 @@ impl Firefly {
         res.error_for_status_ref()?;
         res.json().await
     }
+
+    pub async fn update_transaction(
+        &self,
+        id: &str,
+        txn: &TransactionUpdate,
+    ) -> Result<TransactionSingle, reqwest::Error> {
+        let url = format!("{}/api/v1/transactions/{}", self.url, id);
+        let res = self.client.put(url).json(txn).send().await?;
+        res.error_for_status_ref()?;
+        info!("Successfully updated transaction {}", id);
+        res.json().await
+    }
+
+    pub async fn attach_receipt(
+        &self,
+        id: &str,
+        content: impl Into<reqwest::Body>,
+        filename: impl Into<String>,
+    ) -> Result<(), reqwest::Error> {
+        let filename = filename.into();
+        info!("Attaching receipt {} to transaction {}", filename, id);
+        let url = format!("{}/api/v1/attachments", self.url);
+        let data = AttachmentStore {
+            filename,
+            attachable_type: AttachableType::TransactionJournal,
+            attachable_id: id.into(),
+        };
+        let res = self.client.post(url).json(&data).send().await?;
+        res.error_for_status_ref()?;
+        let attachment: AttachmentSingle = res.json().await?;
+        info!("Created attachment {}", attachment.data.id);
+        let url = format!(
+            "{}/api/v1/attachments/{}/upload",
+            self.url, attachment.data.id
+        );
+        let res = self
+            .client
+            .post(url)
+            .header("Content-Type", "application/octet-stream")
+            .body(content)
+            .send()
+            .await?;
+        res.error_for_status_ref()?;
+        Ok(())
+    }
 }
diff --git a/src/main.rs b/src/main.rs
index 2c3b791..e1408eb 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -7,13 +7,16 @@ use rocket::form::Form;
 use rocket::fs::{FileServer, TempFile};
 use rocket::http::Status;
 use rocket::response::Redirect;
+use rocket::tokio::io::{AsyncReadExt, BufReader};
 use rocket::State;
 use rocket_dyn_templates::{context, Template};
 use serde::Serialize;
 use tracing::{debug, error};
 
 use config::{Config, ConfigError};
-use firefly::{Firefly, TransactionRead};
+use firefly::{
+    Firefly, TransactionRead, TransactionSplitUpdate, TransactionUpdate,
+};
 
 struct Context {
     #[allow(dead_code)]
@@ -47,7 +50,7 @@ pub struct Transaction {
 
 #[derive(rocket::FromForm)]
 struct TransactionPostData<'r> {
-    amount: f32,
+    amount: f64,
     notes: String,
     photo: Vec<TempFile<'r>>,
 }
@@ -64,18 +67,7 @@ impl TryFrom<TransactionRead> for Transaction {
             },
         };
         let date = first_split.date;
-        let amount = t
-            .attributes
-            .transactions
-            .iter()
-            .filter_map(|t| match t.amount.parse::<f64>() {
-                Ok(v) => Some(v),
-                Err(e) => {
-                    error!("Invalid amount: {}", e);
-                    None
-                },
-            })
-            .sum();
+        let amount = t.amount();
         let description = if let Some(title) = &t.attributes.group_title {
             title.into()
         } else {
@@ -158,11 +150,72 @@ async fn get_transaction(id: &str, ctx: &State<Context>) -> Option<Template> {
 
 #[rocket::post("/transactions/<id>", data = "<form>")]
 async fn update_transaction(
-    id: f32,
+    id: &str,
     form: Form<TransactionPostData<'_>>,
-) -> (Status, &'static str) {
-    println!("{} {} {}", id, form.amount, form.photo.len());
-    (Status::ImATeapot, "")
+    ctx: &State<Context>,
+) -> (Status, String) {
+    let txn = match ctx.firefly.get_transaction(id).await {
+        Ok(t) => t.data,
+        Err(e) => {
+            error!("Failed to get transaction {}: {}", id, e);
+            return (Status::NotFound, format!("Invalid transaction {}", id));
+        },
+    };
+    let amount = txn.amount();
+    if amount != form.amount && txn.attributes.transactions.len() != 1 {
+        return (
+            Status::BadRequest,
+            "Cannot update the amount of a split transaction".into(),
+        );
+    }
+    let mut splits: Vec<_> = txn
+        .attributes
+        .transactions
+        .into_iter()
+        .map(|s| TransactionSplitUpdate {
+            transaction_journal_id: s.transaction_journal_id,
+            amount: s.amount,
+            notes: s.notes,
+        })
+        .collect();
+    if let Some(split) = splits.last_mut() {
+        if form.amount != amount {
+            split.amount = form.amount.to_string();
+        }
+        if !form.notes.is_empty() {
+            split.notes = Some(form.notes.clone());
+        }
+    }
+    let update = TransactionUpdate {
+        transactions: splits,
+    };
+    if let Err(e) = ctx.firefly.update_transaction(id, &update).await {
+        error!("Failed to update transaction {}: {}", id, e);
+        return (Status::BadRequest, e.to_string());
+    }
+    for file in &form.photo[..] {
+        let stream = match file.open().await {
+            Ok(f) => f,
+            Err(e) => {
+                error!("Failed to open uploaded file: {}", e);
+                continue;
+            },
+        };
+        let mut reader = BufReader::new(stream);
+        let mut content = Vec::new();
+        if let Err(e) = reader.read_to_end(&mut content).await {
+            error!("Failed to read uploaded file: {}", e);
+            continue;
+        }
+        if let Err(e) = ctx
+            .firefly
+            .attach_receipt(id, content, file.name().unwrap_or("receipt.jpg"))
+            .await
+        {
+            error!("Failed to attach receipt to transaction: {}", e);
+        }
+    }
+    (Status::Ok, "Successfully updated transaction".into())
 }
 
 #[rocket::launch]
diff --git a/templates/transaction.html.tera b/templates/transaction.html.tera
index 38f0ba2..bd891dc 100644
--- a/templates/transaction.html.tera
+++ b/templates/transaction.html.tera
@@ -7,7 +7,7 @@
 <h1>Update Transaction</h1>
 <nav>
   <sl-breadcrumb>
-    <sl-breadcrumb-item href="/">Transactions</sl-breadcrumb-item>
+    <sl-breadcrumb-item href="/transactions">Transactions</sl-breadcrumb-item>
     <sl-breadcrumb-item>{{ description }}</sl-breadcrumb-item>
   </sl-breadcrumb>
 </nav>