Post a manual entry and say why it has no document

Open Bookings and click Manual posting. Pick what happened: Private withdrawal, Private deposit, Reclassification or Correction. Enter the date, an amount and a text. Do not write names, addresses or IBANs in the text; it is stored as a hash.
Every entry needs a document or a reason. Pick the document under Document. With no document, choose No document because and one of the reasons: Document lost (a replacement document is needed), No document is usual (bank fee, toll, parking), Document follows, Reclassification or correction, Year-end closing entry or Private withdrawal or deposit. The four guided entries above carry their own reason, so they ask for neither.
The expert form (Expert form (debit and credit)) always asks for a document or a reason, and for the Reason of the entry.
Click Save as draft, then Post entry and Post now. An entry without a document or a reason cannot be saved or posted; the app tells you to attach a document or choose why there is none. A posted entry is never edited: Reverse (Storno) books the opposite entry once.
Only owners and admins post by hand. Each reason you choose instead of a document is recorded in the audit trail with the entry.