This is an excerpt from 2023 & 2024 NIRSA Flag & Touch Football Rules Book & Officials' Manual-21st Edition by NIRSA.
Section 9. Onside Conversion
Article 1. When Allowed.
A team may elect to attempt an onside conversion at any time in the second half if they score a touchdown unless they are leading by 19 or more points following the Try.
Article 2. Referee’s Responsibility and Team’s Choice.
The Referee must speak to the coach or captain immediately following the Try, asking them whether they would like to attempt an onside conversion from the 20 yard line. Once the coach/captain makes the choice, they may change the decision only when an A or B charged time-out is taken. Possession will be retained by A if the onside conversion results in what would have been a touchdown.
Article 3. Onside Conversion Begins and Ends.
The onside conversion begins when the ball is marked ready for play. The onside conversion ends when B secures possession, the onside conversion is successful, or the ball becomes dead by rule. Neither team can score during the onside conversion.
Article 4. Next Play.
After a successful onside conversion, the ball shall be snapped by the scoring team at their own 30 yard line, unless moved by penalty. After an unsuccessful onside conversion, the ball shall be snapped by the opponent of the touchdown-scoring team at their opponent’s 30 yard line, unless moved by penalty.