diff --git a/lib/RevBank/Cart.pm b/lib/RevBank/Cart.pm
index e22bcd8..1bbf4a6 100644
--- a/lib/RevBank/Cart.pm
+++ b/lib/RevBank/Cart.pm
@@ -82,7 +82,9 @@ sub checkout($self, $user) {
     my $transaction_id = time() - 1300000000;
     RevBank::Plugins::call_hooks("checkout", $self, $user, $transaction_id);
 
-    for my $account (keys %deltas) {
+    for my $account (reverse sort keys %deltas) {
+        # The reverse sort is a lazy way to make the "-" accounts come last,
+        # which looks nicer with the "cash" plugin.
         RevBank::Users::update($account, $deltas{$account}, $transaction_id)
             if $deltas{$account} != 0;
     }
diff --git a/plugins/cash b/plugins/cash
new file mode 100644
index 0000000..684d28c
--- /dev/null
+++ b/plugins/cash
@@ -0,0 +1,42 @@
+#!perl
+
+# Use this plugin for cashbox contents tracking. For it to make sense,
+# you will also need the "deposit_methods" plugin to let users distinguish
+# between cash deposits and other deposit methods.
+
+# This plugin should be loaded *before* the 'stock' plugin in
+# the 'revbank.plugins' configuration file.
+
+HELP1 "cash" => "Checkout without a user account";
+
+sub command :Tab(cash) ($self, $cart, $command, @) {
+    return NEXT if $command ne 'cash';
+
+    if ($cart->size) {
+        $cart->checkout('-cash');
+    } else {
+        call_hooks 'cash';
+    }
+
+    return ACCEPT;
+}
+
+sub hook_cash($class, @) {
+    printf "There should currently be (at least) %s in the cash box.\n",
+        -RevBank::Users::balance("-cash");
+}
+
+sub hook_user_balance($class, $username, $old, $delta, $new, @) {
+    return if $username ne '-cash' or $delta->cents == 0;
+
+    # "-" accounts need to be inverted to display the intuitive value.
+    my $actual_delta = -$delta;
+    my $actual_new   = -$new;
+
+    printf "\nProceed to %s %s %s the cash box;\n  it should then have (at least) %s%s.\n",
+        ($actual_delta->cents < 0 ? "remove" : "put"),
+        abs($delta),
+        ($actual_delta->cents < 0 ? "from" : "into"),
+        $actual_new,
+        ($actual_delta->cents < 0 ? " remaining" : " in it");
+}
diff --git a/plugins/skim b/plugins/skim
index c8e0d93..5563352 100644
--- a/plugins/skim
+++ b/plugins/skim
@@ -13,8 +13,7 @@ sub command :Tab(skim,unskim) ($self, $cart, $command, @) {
 
     $self->{command} = $command;
 
-    printf "There should be (at least) %s in the cashbox.\n",
-        -RevBank::Users::balance("-cash");
+    call_hooks("cash");
 
     return "Amount to $command", \&amount;
 }
diff --git a/plugins/stock b/plugins/stock
index 9f2b5f3..8de3a85 100644
--- a/plugins/stock
+++ b/plugins/stock
@@ -1,13 +1,24 @@
 #!perl
 
-HELP1 "cash" => "Checkout without a user account";
+{
+    # If you want to keep track of stock, you need a way for people to
+    # register cash payments. The 'cash' plugin takes care of that, but
+    # that also assumes deposit_methods. So here's a minimal fallback
+    # implementation for the 'cash' command.
 
-sub command :Tab(cash) ($self, $cart, $command, @) {
-    return NEXT if $command ne 'cash';
+    # If you use the 'cash' plugin, make sure it is loaded *before*
+    # the 'stock' plugin in 'revbank.plugins'.
 
-    $cart->checkout('-cash');
+    HELP1 "cash" => "Checkout without a user account";
 
-    return ACCEPT;
+    sub command :Tab(cash) ($self, $cart, $command, @) {
+        return NEXT if $command ne 'cash';
+        return NEXT if not $cart->size;
+
+        $cart->checkout('-cash');
+
+        return ACCEPT;
+    }
 }
 
 sub hook_checkout($class, $cart, $user, $transaction_id, @) {
diff --git a/revbank.plugins b/revbank.plugins
index 186fc43..30faa9e 100644
--- a/revbank.plugins
+++ b/revbank.plugins
@@ -14,6 +14,8 @@ grandtotal
 take
 split
 #pfand      # makes little sense in a self service environment
+#cash       # cash tracking also requires deposit_methods to make sense
+#skim       # cash tracking also requires deposit_methods to make sense
 stock
 unlisted
 #warnings
@@ -30,5 +32,4 @@ withdraw   # matches amounts
 users      # matches usernames
 deposit    # wants to be after 'users'
 #deposit_methods  # Extra options for 'deposit'. Edit/configure first!
-#skim      # only makes sense if you also use deposit_methods
 #deposit_iban_qr  # QR code display, edit/configure first! (needs qrencode(1))