The London club, who served a transfer ban last summer after breaching FIFA rules on the recruitment of young players, spent just 45 million euros (just over £38million) on Mateo Kovacic but recouped 205m euros in sales (£173.7m).
The CIES Football Observatory found that at the other end of the scale Real Madrid – who paid Chelsea an initial reported 100m euros plus add-ons for Belgian playmaker Eden Hazard last summer – were 181m euros in negative balance when it came to transfers.
Astonishingly, Premier League new boys Aston Villa were second to Real, spending 172m euros and earning just 3m, for a balance of -169m euros.
Premier League clubs had the biggest net deficit of Europe’s big five leagues, spending 844m euros (£715m) more than they earned. Only Ligue 1 showed an overall profit, of 106m euros.
Chelsea were the only Premier League team in the top 10 in terms of net earners, something which should help them post improved financial figures for 2019-20 after recording a loss of £96million for the year ending June 30, 2019.
Benfica, who sold Joao Felix to Atletico Madrid last summer for a reported £113m, were in second place with a net profit of 166m euros, while Ajax were 137m euros up in third after selling star youngsters Matthijs De Ligt and Frenkie De Jong to Juventus and Barcelona respectively.
Villa were joined in the top 10 in terms of negative balance by Manchester United and Tottenham in fourth and fifth respectively, who spent 151m and 141m euros more than they earned.
Arsenal were in 11th place, spending 85m euros more than they earned.