By direct debit, an invoice can be paid directly without the intervention of the customer. This is only possible if a link has been set up via Mollie.
To request a payment by direct debit, use the POST method with, for example, https://api.simplybooks.be/api/v1/invoices/1001?make_direct_collection as the URL.
An example in PHP how a payment can be requested by direct debit:
$email = 'luc@mymail.com';
$password = '123456';
$p = curl_init('https://eenvoudigfactureren.be/api/v1/invoices/1001?make_direct_collection');
curl_setopt($p, CURLOPT_USERPWD, $email . ':' . $password);
curl_setopt($p, CURLOPT_POST, 1);
curl_setopt($p, CURLOPT_RETURNTRANSFER, TRUE);
$result_in_xml_string = curl_exec($p);