Super Bowl LV marked the end of the 2020 NFL season. Now, the 18 NFL teams' goal is to focus on the offseason free agency and legal tampering period. The NFL has listed out estimated dates for their offseason schedule. Here are the important free agency dates to keep an eye out for:2021 NFL free agency start date: March 17Legal tampering period: March 15The 2021 NFL league year starts with the highly-anticipated free agency period on March 17. In the past, the start of the new NFL year was also when free agency began.However, for an added excitement 48 hours before the start of free agency, teams can negotiate with players who will become free agents; this time is referred to as the legal tampering period.The key upcoming dates on the NFL Calendar: 🏈 February 23-March 9: The window to apply franchise or transition tags🏈 March 15-17: Legal negotiating window before free agency🏈 March 17: Free agency and the new league year begin🏈April 29-May 1: The 2021 NFL Draft— Field Yates (@FieldYates) February 9, 2021The purpose of the legal tampering period is to allow agents a two-day timeframe to start discussions with NFL teams.This period provides a chance to get ahead of the tediousness of negotiations. The deal's specificity cannot be agreed on or announced before the official start of free agency.NFL players use agents to handle their negotiations, but if a player represents himself, he must wait to negotiate until the free agency period begins officially on March 17.The legal tampering period of NFL free agency begins six weeks from today.This year could be extra interesting. https://t.co/3AAM3XwM0G— Field Gulls (@FieldGulls) February 1, 2021What happens before NFL free agency starts? Leading up to the beginning of free agency, teams use that opportunity to negotiate with their free agents.Using Dak Prescott as an example: the Dallas Cowboys can consult with Prescott through Super Bowl weekend until the start of free agency. Once the legal tampering window has opened, any team can swoop in and discuss a deal with Prescott or his agent, but only until then.Also Read: Dak Prescott’s Net Worth, Salary, Endorsements and MoreTagging playersIf an NFL team decides they want to keep their players and do not want their free agents to negotiate with other teams, they can apply for a franchise or transition stage.A one-year deal has been made with the franchise and the tagged players, who can continue to negotiate a long-term deal with their franchise but are forbidden to negotiate with other teams.However, the NFL team must decide who they want to tag between February 23 to March 9.Three defensive players were franchise tagged and traded last year, and there are several possibilities again -- a list that includes Yannick Ngakoue, Chris Jones and Matt Judon. @nflnetwork pic.twitter.com/iWNreTxOpa— Tom Pelissero (@TomPelissero) March 3, 2020What happens once NFL free agency begins? Once the competitive free agency begins on March 17, restricted free agents can arrange deals with other franchises. The interested team must extend an offer before the April 23 deadline. Once the request is out there, the previous team has until April 28 to match.The teams involved in signing a restricted free agent must extend the offer sheet ahead of the April 23 deadline. If a team extends an offer, the player's previous team has until April 28 to match the offer or risk losing their player.