...
If a tax credit note had been generated automatically for a credit note, advance payment, or output VAT transaction, all the required fields were filled in.
If you need to create a tax credit note manually, note that the required fields are: Company, Contract, Entity, and Basis.
...
After filling out the tab, click the Save button to save your work. After filling out all the tabs, click Post to post the document without closing it or Post and close to post and close the document.
For descriptions of other buttons, see Document Toolbar.
...