diff --git a/src/overhead_allocation.rs b/src/overhead_allocation.rs
index 898a149..7c43661 100644
--- a/src/overhead_allocation.rs
+++ b/src/overhead_allocation.rs
@@ -4,6 +4,7 @@ use std::{
 };
 
 use csv::Reader;
+use futures::SinkExt;
 use itertools::Itertools;
 use nalgebra::{DMatrix, Dynamic, LU};
 use rayon::prelude::{IntoParallelRefIterator, ParallelIterator};
@@ -331,12 +332,12 @@ where
             .is_some()
             && !overhead_ccs.contains(&line.department)
             && (show_from
-                // When we write out the final amounts rather than changes,
-                // ensure we still output departments that won't be receiving
-                // any costs.
-                || !overhead_other_total
-                    .iter()
-                    .any(|(_, to_department, _)| *to_department == line.department))
+            // When we write out the final amounts rather than changes,
+            // ensure we still output departments that won't be receiving
+            // any costs.
+            || !overhead_other_total
+            .iter()
+            .any(|(_, to_department, _)| *to_department == line.department))
         {
             if show_from {
                 output.serialize(MovedAmount {
@@ -409,7 +410,8 @@ where
                 summed_department_costs: total_cost,
             })
             .collect(),
-        if show_from { Some(output) } else { None },
+        output,
+        show_from,
         zero_threshold,
     )?;
 
@@ -509,7 +511,8 @@ fn remove_quote_and_padding(s: &str) -> String {
 fn reciprocal_allocation_impl(
     allocations: Vec<OverheadAllocationRule>,
     account_costs: Vec<AccountCost>,
-    movement_writer: Option<&mut impl RecordSerializer>,
+    movement_writer: &mut impl RecordSerializer,
+    show_from: bool,
     zero_threshold: f64,
 ) -> anyhow::Result<Vec<AccountCost>> {
     let overhead_department_mappings = get_rules_indexes(&allocations, DepartmentType::Overhead);
@@ -546,6 +549,7 @@ fn reciprocal_allocation_impl(
             overhead_department_mappings,
             allocations,
             movement_writer,
+            show_from,
             zero_threshold,
         )
     } else {
@@ -555,6 +559,7 @@ fn reciprocal_allocation_impl(
             overhead_department_mappings,
             allocations,
             movement_writer,
+            show_from,
             zero_threshold,
         )
     }
@@ -588,7 +593,8 @@ fn do_solve_reciprocal<T: ReciprocalAllocationSolver + Sync + Send>(
     account_costs: Vec<AccountCost>,
     overhead_department_mappings: HashMap<String, usize>,
     allocations: Vec<OverheadAllocationRule>,
-    temp_writer: Option<&mut impl RecordSerializer>,
+    temp_writer: &mut impl RecordSerializer,
+    show_from: bool,
     zero_threshold: f64,
 ) -> anyhow::Result<Vec<AccountCost>> {
     let operating_department_mappings = get_rules_indexes(&allocations, DepartmentType::Operating);
@@ -611,7 +617,7 @@ fn do_solve_reciprocal<T: ReciprocalAllocationSolver + Sync + Send>(
         overhead_department_mappings.len(),
         operating_overhead_mappings,
     );
-    if let Some(temp_writer) = temp_writer {
+    if show_from {
         solve_reciprocal_with_from(
             solver,
             account_costs,
@@ -718,10 +724,10 @@ fn solve_reciprocal_no_from(
                     .map(|cost| TotalDepartmentCost {
                         department: cost.department,
                         value: cost.value, // + if new_cost == 0_f64 || diff == 0_f64 {
-                                           //     0_f64
-                                           // } else {
-                                           //     cost.value / new_cost * diff
-                                           // },
+                        //     0_f64
+                        // } else {
+                        //     cost.value / new_cost * diff
+                        // },
                     })
                     .filter(|cost| cost.value != 0_f64)
                     .collect(),
@@ -778,12 +784,12 @@ fn solve_reciprocal_with_from<T: ReciprocalAllocationSolver + Sync + Send>(
             temp_writer.serialize(moved_amount)?;
         }
     }
+    temp_writer.flush()?;
     Ok(())
 }
 
 #[cfg(test)]
 mod tests {
-
     use crate::reciprocal_allocation;
     use crate::AccountCost;
     use crate::DepartmentType;
@@ -871,10 +877,11 @@ mod tests {
         let result = reciprocal_allocation_impl(
             allocation_rules,
             initial_totals,
-            Some(&mut movement_writer),
+            &mut movement_writer,
+            false,
             0.00001,
         )
-        .unwrap();
+            .unwrap();
         assert_eq!(expected_final_allocations, result);
     }