Kieran Trippier told a friend to "lump on" his £20million transfer from Tottenham Hotspur to Atletico Madrid, according to the Football Association's independent regulatory commission.
Atletico are appealing the 10-week ban given to Trippier by the FA in December for breaking gambling rules.
The suspension is currently on hold until world football's governing body FIFA hear the appeal.
In the meantime, the FA has published full details of its independent investigation into the England international.
In the written reasons for their decision, the independent commission rejected Trippier's claim that the messages were simply "banter".
Tripper left Spurs to join Atletico in the summer of 2019 after four years at the club.
He is said to have told friend Oliver Hawley “it’s happening” in a text conversation, prompting him to place two bets, one of £65 at odds of 7/2 and one bet of £40 at 9/4.
And in a group chat on WhatsApp, Trippier wrote “the clock is ticking get this deal done” after being given permission to travel to Spain to complete his transfer.
This is said to have led to more bets being placed.
According to the evidence, Hawley placed bets of £100, £120, £8.75, £20 and £300, while other friends also put money on the deal on July 15.
The transfer and fee was agreed on July 16, and announced the following day.
Another friend, Matthew Brady, asked Trippier: “Shall I lump on you going there?” Trippier replied: “Can do mate".
When he was asked: “100 per cent, Tripps?” The full-back replied: “Yeah mate.”
He later added: “Lump on if you want mate.”
Trippier, who was also fined £70,000, received witness statements in his defence from the likes of former Tottenham team-mate Harry Kane, England boss Gareth Southgate and Sean Dyche, who managed him at Burnley.
