diff --git a/reportbuilder/classes/local/aggregation/base.php b/reportbuilder/classes/local/aggregation/base.php
index 9cb1167aa6a..77409aa35f0 100644
--- a/reportbuilder/classes/local/aggregation/base.php
+++ b/reportbuilder/classes/local/aggregation/base.php
@@ -133,7 +133,7 @@ abstract class base {
     public static function format_value($value, array $values, array $callbacks, int $columntype) {
         foreach ($callbacks as $callback) {
             [$callable, $arguments] = $callback;
-            $value = ($callable)($value, (object) $values, $arguments);
+            $value = ($callable)($value, (object) $values, $arguments, static::get_class_name());
         }
 
         return $value;
diff --git a/reportbuilder/classes/local/report/column.php b/reportbuilder/classes/local/report/column.php
index 5db3f8dd2c4..3db57db8ba5 100644
--- a/reportbuilder/classes/local/report/column.php
+++ b/reportbuilder/classes/local/report/column.php
@@ -473,18 +473,20 @@ final class column {
     }
 
     /**
-     * Adds column callback (in the case there are multiple, they will be applied one after another)
+     * Adds column callback (in the case there are multiple, they will be called iteratively - the result of each passed
+     * along to the next in the chain)
      *
      * The callback should implement the following signature (where $value is the first column field, $row is all column
-     * fields, and $additionalarguments are those passed on from this method):
+     * fields, $additionalarguments are those passed to this method, and $aggregation indicates the current aggregation type
+     * being applied to the column):
+     *
+     * function($value, stdClass $row, $additionalarguments, ?string $aggregation): string
      *
      * The type of the $value parameter passed to the callback is determined by calling {@see set_type}, this type is preserved
-     * if the column is part of a report source and is being aggregated.
-     * For entities that can to be left joined to a report, the first argument to their column callbacks must be nullable.
+     * if the column is part of a report source and is being aggregated. For entities that can be left joined to a report, the
+     * first argument of the callback must be nullable (as it should also be if the first column field is itself nullable).
      *
-     * function($value, stdClass $row[, $additionalarguments]): string
-     *
-     * @param callable $callable function that takes arguments ($value, \stdClass $row, $additionalarguments)
+     * @param callable $callable
      * @param mixed $additionalarguments
      * @return self
      */
@@ -687,7 +689,7 @@ final class column {
         } else {
             foreach ($this->callbacks as $callback) {
                 [$callable, $arguments] = $callback;
-                $value = ($callable)($value, (object) $values, $arguments);
+                $value = ($callable)($value, (object) $values, $arguments, null);
             }
         }
 
diff --git a/reportbuilder/tests/local/aggregation/avg_test.php b/reportbuilder/tests/local/aggregation/avg_test.php
index 661c2129d5a..86123c3c7de 100644
--- a/reportbuilder/tests/local/aggregation/avg_test.php
+++ b/reportbuilder/tests/local/aggregation/avg_test.php
@@ -23,6 +23,7 @@ use core_reportbuilder_generator;
 use core_reportbuilder\manager;
 use core_reportbuilder\local\report\column;
 use core_user\reportbuilder\datasource\users;
+use stdClass;
 
 defined('MOODLE_INTERNAL') || die();
 
@@ -100,19 +101,20 @@ class avg_test extends core_reportbuilder_testcase {
         $instance = manager::get_report_from_persistent($report);
         $instance->get_column('user:suspended')
             ->set_type(column::TYPE_FLOAT)
-            ->set_callback(static function(float $value): string {
-                return number_format($value, 1) . ' suspended';
+            ->set_callback(static function(float $value, stdClass $row, $arguments, ?string $aggregation): string {
+                // Simple callback to return the given value, and append aggregation type.
+                return number_format($value, 1) . " ({$aggregation})";
             });
 
         $content = $this->get_custom_report_content($report->get('id'));
         $this->assertEquals([
             [
                 'c0_firstname' => 'Admin',
-                'c1_suspended' => '0.0 suspended',
+                'c1_suspended' => '0.0 (avg)',
             ],
             [
                 'c0_firstname' => 'Bob',
-                'c1_suspended' => '0.5 suspended',
+                'c1_suspended' => '0.5 (avg)',
             ],
         ], $content);
     }
diff --git a/reportbuilder/tests/local/aggregation/groupconcat_test.php b/reportbuilder/tests/local/aggregation/groupconcat_test.php
index f945eab16e9..94b6e9643e7 100644
--- a/reportbuilder/tests/local/aggregation/groupconcat_test.php
+++ b/reportbuilder/tests/local/aggregation/groupconcat_test.php
@@ -22,7 +22,9 @@ use core_badges_generator;
 use core_badges\reportbuilder\datasource\badges;
 use core_reportbuilder_testcase;
 use core_reportbuilder_generator;
+use core_reportbuilder\manager;
 use core_user\reportbuilder\datasource\users;
+use stdClass;
 
 defined('MOODLE_INTERNAL') || die();
 
@@ -132,16 +134,24 @@ class groupconcat_test extends core_reportbuilder_testcase {
             'aggregation' => groupconcat::get_class_name(),
         ]);
 
+        // Add callback to format the column.
+        $instance = manager::get_report_from_persistent($report);
+        $instance->get_column('user:confirmed')
+            ->add_callback(static function(string $value, stdClass $row, $arguments, ?string $aggregation): string {
+                // Simple callback to return the given value, and append aggregation type.
+                return "{$value} ({$aggregation})";
+            });
+
         // Assert confirmed column was aggregated, and sorted predictably with callback applied.
         $content = $this->get_custom_report_content($report->get('id'));
         $this->assertEquals([
             [
                 'c0_firstname' => 'Admin',
-                'c1_confirmed' => 'Yes',
+                'c1_confirmed' => 'Yes (groupconcat)',
             ],
             [
                 'c0_firstname' => 'Bob',
-                'c1_confirmed' => 'No, Yes, Yes',
+                'c1_confirmed' => 'No (groupconcat), Yes (groupconcat), Yes (groupconcat)',
             ],
         ], $content);
     }
diff --git a/reportbuilder/tests/local/aggregation/groupconcatdistinct_test.php b/reportbuilder/tests/local/aggregation/groupconcatdistinct_test.php
index f68459010b0..0477ba8a423 100644
--- a/reportbuilder/tests/local/aggregation/groupconcatdistinct_test.php
+++ b/reportbuilder/tests/local/aggregation/groupconcatdistinct_test.php
@@ -20,8 +20,10 @@ namespace core_reportbuilder\local\aggregation;
 
 use core_reportbuilder_testcase;
 use core_reportbuilder_generator;
+use core_reportbuilder\manager;
 use core_reportbuilder\local\report\column;
 use core_user\reportbuilder\datasource\users;
+use stdClass;
 
 defined('MOODLE_INTERNAL') || die();
 
@@ -142,16 +144,24 @@ class groupconcatdistinct_test extends core_reportbuilder_testcase {
             'aggregation' => groupconcatdistinct::get_class_name(),
         ]);
 
+        // Add callback to format the column.
+        $instance = manager::get_report_from_persistent($report);
+        $instance->get_column('user:confirmed')
+            ->add_callback(static function(string $value, stdClass $row, $arguments, ?string $aggregation): string {
+                // Simple callback to return the given value, and append aggregation type.
+                return "{$value} ({$aggregation})";
+            });
+
         // Assert confirmed column was aggregated, and sorted predictably with callback applied.
         $content = $this->get_custom_report_content($report->get('id'));
         $this->assertEquals([
             [
                 'c0_firstname' => 'Admin',
-                'c1_confirmed' => 'Yes',
+                'c1_confirmed' => 'Yes (groupconcatdistinct)',
             ],
             [
                 'c0_firstname' => 'Bob',
-                'c1_confirmed' => 'No, Yes',
+                'c1_confirmed' => 'No (groupconcatdistinct), Yes (groupconcatdistinct)',
             ],
         ], $content);
     }
diff --git a/reportbuilder/tests/local/aggregation/sum_test.php b/reportbuilder/tests/local/aggregation/sum_test.php
index 56b4fb7efd0..c8b8aaa467e 100644
--- a/reportbuilder/tests/local/aggregation/sum_test.php
+++ b/reportbuilder/tests/local/aggregation/sum_test.php
@@ -23,6 +23,7 @@ use core_reportbuilder_generator;
 use core_reportbuilder\manager;
 use core_reportbuilder\local\report\column;
 use core_user\reportbuilder\datasource\users;
+use stdClass;
 
 defined('MOODLE_INTERNAL') || die();
 
@@ -101,19 +102,20 @@ class sum_test extends core_reportbuilder_testcase {
         $instance = manager::get_report_from_persistent($report);
         $instance->get_column('user:suspended')
             ->set_type(column::TYPE_INTEGER)
-            ->set_callback(static function(int $value): string {
-                return "{$value} suspended";
+            ->set_callback(static function(int $value, stdClass $row, $arguments, ?string $aggregation): string {
+                // Simple callback to return the given value, and append aggregation type.
+                return "{$value} ({$aggregation})";
             });
 
         $content = $this->get_custom_report_content($report->get('id'));
         $this->assertEquals([
             [
                 'c0_firstname' => 'Admin',
-                'c1_suspended' => '0 suspended',
+                'c1_suspended' => '0 (sum)',
             ],
             [
                 'c0_firstname' => 'Bob',
-                'c1_suspended' => '2 suspended',
+                'c1_suspended' => '2 (sum)',
             ],
         ], $content);
     }
diff --git a/reportbuilder/tests/local/report/column_test.php b/reportbuilder/tests/local/report/column_test.php
index 721b1a7b3b8..c9483005f3a 100644
--- a/reportbuilder/tests/local/report/column_test.php
+++ b/reportbuilder/tests/local/report/column_test.php
@@ -419,6 +419,22 @@ class column_test extends advanced_testcase {
         ]));
     }
 
+    /**
+     * Test that column value with callback (where aggregation is not set) is returned
+     */
+    public function test_format_value_callback_aggregation(): void {
+        $column = $this->create_column('test')
+            ->set_index(1)
+            ->add_field('t.foo')
+            ->set_type(column::TYPE_INTEGER)
+            ->add_callback(static function(int $value, stdClass $values, $argument, ?string $aggregation): string {
+                // Simple callback to return the given value, and append type of aggregation parameter.
+                return "{$value} " . gettype($aggregation);
+            });
+
+        $this->assertEquals("42 NULL", $column->format_value(['c1_foo' => 42]));
+    }
+
     /**
      * Test adding multiple callbacks to a column
      */
diff --git a/reportbuilder/upgrade.txt b/reportbuilder/upgrade.txt
index da502fc9e4d..6d8b50f7a73 100644
--- a/reportbuilder/upgrade.txt
+++ b/reportbuilder/upgrade.txt
@@ -4,6 +4,8 @@ Information provided here is intended especially for developers.
 === 4.2 ===
 
 * New method `set_checkbox_toggleall` in system report class to allow reports to easily create checkbox toggle columns
+* Column callbacks are now passed a fourth argument to indicate the aggregation type currently being applied, which allows
+  for columns to define how the aggregated data is displayed
 * New methods `[add|get]_attributes` added to report base class, for including custom attributes in report container HTML
 * The following attributes can be added to custom reports in order to control card view display (via the `add_attributes` method):
   - `data-force-card` to force cards view