Hi @VsoMDjewP 

Can you please check and let me know whether you have followed the below mentioned steps ? 

Steps to follow:

1. Open Manual Customer Invoice window.
2. Click New to create new record.
3. Enter the Customer ID which you have created before.
4. Enter the invoice ID as ‘XXXXXX’.
5. Go to the Lines tab and create a new record.
6. Enter the Tax code
7. Add the Gross amount or the Net Amount as per your setup.
8. Go to Posting tab and click new to create new record.
9. Add ‘XXXX’ as Account. (Account Number)
10. Enter the amount ‘-XXX’ in the “Amount” column in the Posting tab.
11. Save the Invoice.
12. Note that the status of the invoice will be Preliminary.
13. Then RMB on the header select Post invoice. Then the Invoice status will be changed to PostedAuth.

If you still don’t see or have the post invoice Option after following these steps. Try below mentioned methods,

1. Go to Voucher Series per voucher type window > Search for Voucher type F > RMB on the 2021 line and select User Group per voucher series > There check whether the Authorization Level of the User group you belong is Enter and Approve. If not set it to Enter and Approve.
2. If 1st is already in place, try by adding your user in the Invoice Posting Authorizers window. That might help

Please follow these and let me know the result.

Best Regards,

Peshala