diff --git a/rattail_corepos/corepos/office/scripts/update-fannie-config.php b/rattail_corepos/corepos/office/scripts/update-fannie-config.php
new file mode 100644
index 0000000..9b101e0
--- /dev/null
+++ b/rattail_corepos/corepos/office/scripts/update-fannie-config.php
@@ -0,0 +1,40 @@
+<?php
+
+$options = getopt('h', array(
+    'help',
+    'path:',
+    'name:',
+    'value:',
+));
+
+$help = isset($options['h']) or isset($options['help']);
+$path = isset($options['path']) ? $options['path'] : null;
+$name = isset($options['name']) ? $options['name'] : null;
+$value = isset($options['value']) ? $options['value'] : null;
+
+if ($help or !$path or !$name or !$value) {
+    $script = basename($argv[0]);
+    echo "Usage:  $script --path FANNIE_CONFIG_PATH --name SETTING_NAME --value SETTING_VALUE\n";
+    exit($help ? 0 : 1);
+}
+
+if (!is_file(realpath($path))) {
+    echo "Config file does not exist: $path\n";
+    exit(2);
+}
+$path = realpath($path);
+
+// convert value from JSON to PHP
+$value = json_decode($value);
+if (gettype($value) == 'string') {
+    $value = "'$value'";
+} else {
+    echo gettype($value) . " data type not supported: " . print_r($value, true);
+    exit(2);
+}
+
+// invoke native CORE logic to update config file
+require(dirname($path) . '/install/util.php');
+confset($name, $value);
+
+?>
diff --git a/rattail_corepos/corepos/office/util.py b/rattail_corepos/corepos/office/util.py
index c2c7426..2d70e34 100644
--- a/rattail_corepos/corepos/office/util.py
+++ b/rattail_corepos/corepos/office/util.py
@@ -31,7 +31,7 @@ import subprocess
 from rattail.files import resource_path
 
 
-def get_fannie_config_value(config, name):
+def get_fannie_config_value(config, name, fannie_config_path=None):
     """
     Retrieve a config value from `fannie/config.php`
 
@@ -40,6 +40,9 @@ def get_fannie_config_value(config, name):
     :param name: Name of the config value to be returned.  This need
        not be prefixed with ``FANNIE_`` although it can be.
 
+    :param fannie_config_path: Optional path to fannie config file.
+       If not specified, it is will be determined via ``config``.
+
     :returns: Config value as Python object, e.g. a string or dict.
        This is believed to work okay but since the Fannie config file
        represents data with PHP code, which is then converted to JSON
@@ -48,20 +51,53 @@ def get_fannie_config_value(config, name):
     if not name.startswith('FANNIE_'):
         name = f'FANNIE_{name}'
 
-    is4c = config.require('corepos', 'srcdir')
-    path = os.path.join(is4c, 'fannie', 'config.php')
+    if not fannie_config_path:
+        is4c = config.require('corepos', 'srcdir')
+        fannie_config_path = os.path.join(is4c, 'fannie', 'config.php')
     script = resource_path('rattail_corepos.corepos.office:scripts/parse-fannie-config.php')
 
     try:
         output = subprocess.check_output(['php', script,
-                                          '--path', path,
+                                          '--path', fannie_config_path,
                                           '--setting', name])
     except subprocess.CalledProcessError as error:
-        raise ValueError(f"failed to read value: {error.output.decode('utf_8')}")
+        output = error.output.decode('utf_8')
+        if "file does not contain setting" in output:
+            raise ValueError(output)
+        raise
 
     return json.loads(output.decode('utf_8'))
 
 
+def set_fannie_config_value(config, name, value, fannie_config_path=None):
+    """
+    Update a config value in `fannie/config.php`
+
+    :param config: Rattail config object.
+
+    :param name: Name of the config value to set.  This need not be
+       prefixed with ``FANNIE_`` although it can be.
+
+    :param value: Config value to set This must be provided as a
+       JSON-compatible string.
+
+    :param fannie_config_path: Optional path to fannie config file.
+       If not specified, it is will be determined via ``config``.
+    """
+    if not name.startswith('FANNIE_'):
+        name = f'FANNIE_{name}'
+
+    if not fannie_config_path:
+        is4c = config.require('corepos', 'srcdir')
+        fannie_config_path = os.path.join(is4c, 'fannie', 'config.php')
+    script = resource_path('rattail_corepos.corepos.office:scripts/update-fannie-config.php')
+
+    output = subprocess.check_output(['php', script,
+                                      '--path', fannie_config_path,
+                                      '--name', name,
+                                      '--value', json.dumps(value)])
+
+
 def get_blueline_template(config):
     return get_fannie_config_value(config, 'BLUELINE_TEMPLATE')