I need help regarding the billing voucher code

[secureweb16]

Are voucher codes possible when booking a plan? If so, how does Shopify know which code works and what value it has? Please let me
know the solutions that are possible, If yes then please share it's related information. How it will done using this package.

I have tried to find the details, But the related information is not available.

Currently, I have simply passed the plan ID and how it will work with the discount code.

<p><a href="{{ route('billing', ['plan' => 2, 'shop' => Auth::user()->name, 'host' => app('request')->input('host') ]) }}">Upgrade</a></p>