The 25-year-old moved to Turf Moor from Griffin Park in 2016 and has made a name for himself as one of the brightest defenders in the Premier League.
Tarkowski's rise at club level has culminated in a starting appearance for the Three Lions in Tuesday night's 1-1 friendly draw with Italy at Wembley.
According to Sky Sports News, a number of clauses linked to international achievements were inserted into Tarkowski's contract when the defender moved to Burnley.
The report claims that Brentford are due £500,000 per friendly start and £250,000 per substitute appearance, while competitive starts would yield £1,000,000 and sub appearances £500,000.
However, the payments are believed to be capped at £1m regardless of the combination of clauses activated by the player.
Tarkowski started in a back three as Gareth Southgate's England side took the lead against the 2006 World Cup winners, but Lorenzo Insigne equalised three minutes from time with a controversial penalty.