diff --git a/src/main.rs b/src/main.rs
index 462ddc8..01daa25 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,4 +1,4 @@
-use std::path::PathBuf;
+use std::{fs::File, io::BufWriter, path::PathBuf};
 
 use clap::{Parser, Subcommand};
 
@@ -69,8 +69,11 @@ enum Commands {
         #[arg(short, long, default_value = "0.00000000000000001")]
         zero_threshold: f64,
 
-        #[arg(short, long, value_name = "FILE")]
-        output: Option<PathBuf>,
+        #[arg(short, long, value_name = "FILE", default_value = "alloc_output.csv")]
+        output: PathBuf,
+
+        #[arg(short, long)]
+        msgpack_serialisation: bool,
     },
     CreateProducts {
         #[arg(short, long, value_name = "FILE")]
@@ -129,20 +132,41 @@ fn main() -> anyhow::Result<()> {
             show_from,
             zero_threshold,
             output,
-        } => coster_rs::reciprocal_allocation(
-            &mut csv::Reader::from_path(lines)?,
-            &mut csv::Reader::from_path(accounts)?,
-            &mut csv::Reader::from_path(allocation_statistics)?,
-            &mut csv::Reader::from_path(areas)?,
-            &mut csv::Reader::from_path(cost_centres)?,
-            &mut csv::Writer::from_path(output.unwrap_or(PathBuf::from("alloc_output.csv")))?,
-            use_numeric_accounts,
-            exclude_negative_allocation_statistics,
-            true,
-            account_type,
-            show_from,
-            zero_threshold,
-        ),
+            msgpack_serialisation,
+        } => {
+            if msgpack_serialisation {
+                let mut file = BufWriter::new(File::create(output)?);
+                coster_rs::reciprocal_allocation(
+                    &mut csv::Reader::from_path(lines)?,
+                    &mut csv::Reader::from_path(accounts)?,
+                    &mut csv::Reader::from_path(allocation_statistics)?,
+                    &mut csv::Reader::from_path(areas)?,
+                    &mut csv::Reader::from_path(cost_centres)?,
+                    &mut rmp_serde::Serializer::new(&mut file),
+                    use_numeric_accounts,
+                    exclude_negative_allocation_statistics,
+                    true,
+                    account_type,
+                    show_from,
+                    zero_threshold,
+                )
+            } else {
+                coster_rs::reciprocal_allocation(
+                    &mut csv::Reader::from_path(lines)?,
+                    &mut csv::Reader::from_path(accounts)?,
+                    &mut csv::Reader::from_path(allocation_statistics)?,
+                    &mut csv::Reader::from_path(areas)?,
+                    &mut csv::Reader::from_path(cost_centres)?,
+                    &mut csv::Writer::from_path(output)?,
+                    use_numeric_accounts,
+                    exclude_negative_allocation_statistics,
+                    true,
+                    account_type,
+                    show_from,
+                    zero_threshold,
+                )
+            }
+        }
         Commands::CreateProducts {
             definitions,
             encounters,
diff --git a/src/overhead_allocation.rs b/src/overhead_allocation.rs
index fa8fa11..e5ba2f5 100644
--- a/src/overhead_allocation.rs
+++ b/src/overhead_allocation.rs
@@ -780,7 +780,6 @@ impl<W: Write> RecordSerializer for Serializer<W> {
 
 #[cfg(test)]
 mod tests {
-    use std::fs::File;
 
     use crate::reciprocal_allocation;
     use crate::AccountCost;
@@ -789,7 +788,6 @@ mod tests {
     use crate::TotalDepartmentCost;
 
     use super::reciprocal_allocation_impl;
-    use super::MovedAmount;
 
     #[test]
     fn test_basic() {