app/Http/Controllers/Settings/SubscriptionController.php
public function downloadInvoice(Request $request, $invoiceId)
    {
        $data = array_merge([
            'vendor' => 'Vendor',
            'product' => 'Product',
            'vat' => new ViewExpression(nl2br(e($request->user()->extra_billing_info))),
        ], Spark::generateInvoicesWith());

        return Auth::user()->downloadInvoice($invoiceId, $data);
    }
public function downloadInvoice(Request $request, $invoiceId)
    {
        $data = array_merge([
            'vendor' => 'Vendor',
            'product' => 'Product',
            'vat' => new ViewExpression(nl2br(e($request->user()->extra_billing_info))),
        ], Spark::generateInvoicesWith());

        return Auth::user()->downloadInvoice($invoiceId, $data);
    }
Download the given invoice for the user.

@param  string  $invoiceId
@return \Illuminate\Http\Response