It gets annoying though when you have just single invoices or documents that don't quite fit in your structure. I eventually started throwing all received documents in one folder and used the name as tags basically. E.g. 20210214_plumber_invoice.pdf or 20181204_someshop_invoice_playstation.pdf... (And yes I use the filename for tagging because I don't trust e.g. Windows tagging system to be there forever or be copied properly onto other operating systems.)