If a member requires an additional item (to the standard category items) added to their invoice, this can be added in the Items section in the Membership tab under Members:
For example, the following member wants the "Trundler Shed" item added to their invoice for the year. Simply add "Trundler Shed" to his item list, and assign the appropriate dates and price.
NOTE: The key thing here when doing this for renewal time, is to ensure you select the correct Start and End date. Aligning this to the correct renewal dates for the member will allow this to be re-invoiced the following year in alignment with the subscription date renewal items.
Then, when you are ready to do the Process Renewals (for the bulk invoice run), you should see this item as part of the member subscription invoice e.g.