Registering for an event is synonymous with buying a ticket to the event. Event capacities are managed by limiting the number of tickets that are for sale. There are three approaches:
Automatic ticketing is the default, and requires no special effort on your part to set up. If the event turns out to be unmanageably popular, you can manually close sales by configuring the fee, and checking off the "sold out" option.
GA ticketing is used for events that have limited seating. You can pre-issue a number of tickets equal to the event capacity, and the registration system is not able to sell any more. You can always issue more tickets later if you are able to secure a venue with larger capacity.
Special ticketing is used for specific registration categories that have limits. The special ticket limits are in addition to the GA limits. In other words, the total event attendance can be the GA tickets plus the special tickets.
Example: a banquet has a total seating capacity of 200. The head table is for VIPs only, but there are only 16 VIP seats available. You could set this up as 16 special tickets for the VIP fee, plus 184 (ie. 200–16) GA tickets for the rest of the banquet. This set-up ensures that you cannot oversell either the VIP table, or the event overall.
Tickets can be in different states, depending on where they are in the sales cycle:
The registration automatically manages these ticket states, so you should not have to concern yourself with the details. The important states are confirmed and reserved, both of which are treated as completed registrations.
Unsold tickets will automatically be recycled, as needed. On-hold tickets and canceled tickets will be re-used if there are no more active tickets to pull from.
If you select either GA or special ticketing, you will first have to generate your ticket inventory before you can sell any. Go to the ticketing tool, and select the Issue new tickets pane. Specify how many tickets you want to create, and whether you want to release them for sale immediately, or hold them back until later. You can issue more tickets at later times, such as if you increase your event capacity.
If you hold any tickets back, you can release them at a later time under the Release tickets pane.
If you decide that tickets are selling too fast, and you want to hold some back, you can pull them from circulation under the Withdraw tickets pane.
If you have a mix of GA and special tickets, you can also move tickets back and forth between those categories to manage your ticket availability.
Note that some ticket management management functions can only be performed on inactive tickets, just to make sure you aren't changing ticket configurations at the same time someone is trying to buy them. So you may need to withdraw tickets from sale first before making further adjustments.
Note that tickets can be temporarily unavailable after they have been added to a shopping cart. If the purchaser doesn't follow through with their purchase, those on-hold tickets will eventually be released for re-sale. (You can manually tell the system to release any unsold held tickets, using a button under the Release tickets pane.)
If there are no tickets available, public registration screens will automatically indicate that the event is sold out.
Note that sell-outs can sometimes be temporary. Tickets may be tied up in shopping carts where the purchase ultimately fails. Other ticket sales can be canceled for other reasons. In both cases, those tickets will automatically get recycled, and the formerly sold-out event will automatically open again.
If you expand capacity, you can go to your ticketing screen and issue new tickets in an appropriate quantity to restart sales.
You can optionally enable waitlisting on fees where you anticipate both selling out and the ability to expand capacity. In your fee configuration, check off Enable waitlist when sold out. This will run registrants through a pseudo-registration process so that you have some indication of who is interested in attending even when you don't have the capacity to accept them.
Later, if you do decide to expand capacity, you don't even have to issue new tickets, as you will have already collected the waitlist registrations. You can go to your waitlist management tools, and convert those waitlist registrations to proper registrations. If you still have more space after doing this, you can then issue the remaining spaces as new tickets. Registration should automatically re-open when those tickets become available.