Uefa initially opened an investigation into PSG's spending in September 2017 under pressure from some of Europe's biggest clubs
Uefa said Monday it had ordered accusations that Paris Saint-Germain has broken its financial fair play rules to be referred to its financial unit "for further investigation".
European football's governing body initially opened an investigation into the Qatari-owned club's spending in September 2017 under pressure from some of Europe's biggest clubs after the French club signed Brazilian midfielder Neymar for a world-record 222m euros ($261m).
Within weeks the club had also agreed a deal to sign teenage striker Kylian Mbappe from Monaco for 180m euros. He has since become one of world football's hottest properties.
In June, Uefa's Club Financial Control Body (CFCB) closed its investigation into PSG's spending only to re-open it just a month later.
UEFA said on Monday the case had now been referred "back to the CFCB Investigatory Chamber for further investigation".
UEFA rules mandate that clubs cannot spend more than they earn in any given season and deficits must fall within a 30-million-euro limit over three seasons.
PSG's case is complicated by its lucrative sponsorship deals with Qatar National Bank and the Gulf state's tourism authority.
If eventually found guilty PSG could face exclusion from European competition for one or more seasons, a huge blow to the club's Qatari owners who have made winning the Champions League their key goal.