When you wish to enter invoices for items that you are not selling for example utility bills, rent, equipment, marketing expenses etc, you use the SP Ledger (Sales Purchase Ledger). This video explains the process and there are step by step instructions below the video.
Steps
In Accounts, open the S/P Ledger screen.
Enter Edit mode.
Use the New button to add a new entry.
Select the Supplier from the lookup.
Leave the Post as ticked as this will post the entry to the accounts whne the entry is saved.
If the Crd column is ticked, this indicates that the entry is a credit, i.e. the supplier owes you.
If the entry is for a supplier who uses a non-base currency, then the currency they use will be displayed here and you can update the exchange rate being used for the entry.
Select the Nominal Account to post the entry to.
Record the supplier's Invoice Ref and select a date for the invoice.
Assign a Nominal Classification for the entry (optional).
Enter either the gross or net invoice total.
Check the Tax Rate in the drop down.
Add a description and status note (optional) for the entry.
Save the screen to commit the entry to the accounts.
Notes/Caveats
Note that although you can enter sales via the SP Ledger this is very rare. Normally, sales should be entered using sales orders so that you have an audit trail on the customers record.