Hello,
Try this:
{
"processDefinitionKey":"invoicesApprovalProcess",
"businessKey":"A1234567",
"invoiceNumber":"A1234567",
"invoiceAmount":"123",
"supplierName":"supplierName",
"supplierNif":"supplierNif",
"supplierId":"supplierId",
"companyName":"companyName",
"companyNif":"companyNif",
"companyId":"companyId",
"approver":"kermit"
}
Regards