There are three types of STP messages you can send from Lightning Payroll: a New Event, an Adjust Event, and an Update Event.
A New Event is the most common submission type and is the recommended way to send Single Touch information to the ATO; it basically means you are submitting new pay information. a New Event will automatically be suggested by Lightning Payroll the first time (based on processed date) you submit a pay run.
Adjust Events are a more recent option, which are particularly helpful in that they update and adjust pre-filled BAS totals, unlike Update Events. Adjust Events allow you to adjust the total gross (W1) and total tax (W2) of a pay run, when changes have been made after having already sent a New Event. These events can be done as either a positive or negative dollar value, and relate to the pay run totals as a whole, not to individual employees. Read more about the specifics of Adjust Events here.
Update Events are also used to submit amendments made to pay runs already lodged as a New Event. They can also be used for submitting YTD figures for terminated staff who are not available for a New Event submission due to not being paid within the pay period being lodged. This is particularly useful at end of financial year to ensure all employees are being finalised, and not just the employees on the final pay run of the financial year; this is why we ask you to submit your end of financial year STP twice - first as a New Event, then as an Update Event.
New Events should not be regularly sent for pay runs processed/paid in the past. The ATO will allow past processed dates on new/pay events, but they discourage it. It is best practice to submit STP regularly when you pay your employees, in chronological order by processed date (pay run dates are irrelavant to STP).
Update Events cannot be sent for pays processed/paid in the future.
Lightning Payroll collects YTD values using the pay processed/paid date, and lodges using the pay period's most recent processed date within the same financial year.
For more information on STP events and guidelines, see here.