Leagues can choose to use the new handball law when the season resumes, football’s lawmaking body says.

The International Football Association Board (Ifab) wrote to the four British football associations on Tuesday to confirm the approved changes to the laws of the game for 2020-21.

This includes using the “T-shirt line” to differentiate between the arm and the shoulder for handball decisions.

New laws usually become compulsory on 1 June for the start of the new season.

However, because of the unprecedented circumstances presented by coronavirus, competitions will get the choice of whether to implement them for the rest of this season.

In official communication seen by BBC Sport, Ifab said: “Competitions which have been suspended because of Covid-19 have the option of completing the competition using the Laws of the Game 2019-20 or adopting the Laws of the Game 2020-21.

“Friendly/practice/warm-up matches in preparation for the restart of the competition are permitted to use the version of the Laws that will be used when the competition restarts.”

The member associations will now pass this guidance on to the competitions, who will make their own decisions on which rules to use at the point football resumes.

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The change to the handball rule was the most significant alteration to the laws of the game that came out of Ifab’s annual general meeting (AGM) in February.

Irish FA chief executive Patrick Nelson explained the importance of the change at Ifab’s recent AGM, saying “the shoulder itself doesn’t really have an opportunity to make the body bigger whereas the arms do”.

The “T-shirt line” or armpit – essentially where the sleeve on a T-shirt ends – will become a key marker on the player’s body for match officials, with anything below that being handball.

Jonathan Ford, chief executive of the Football Association of Wales, explained the law change as “basically a clarification as to where exactly does the arm start in the case of handball and where does the shoulder finish”.

Before the suspension of football, the Premier League game between Burnley and Bournemouth highlighted the confusion with the current distinction between the arm and shoulder, with two contentious handball decisions made by the video assistant referee.

The handball law had previously been changed so that a handball would be given against a player if their arms extended “beyond a natural silhouette”.