Arsenal have revealed a pre-tax loss of £23.5m for the year to 31 May, compared with a £97.4m profit 12 months earlier.
The reversal is attributed to revenue from outgoing transfers reducing from £122.3m to £16.8m.
The Premier League club says average annual profit club from player sales over the past five seasons, including 2019-20, is £34m.
Playing in the Europa League rather than the Champions League had an "adverse impact".
Arsenal also confirmed their fifth-placed finish last season was below the pre-season target of securing a return to the Champions League after a two-year absence.
The details of Arsenal's matchday revenue will only be known when Arsenal Holdings releases its figures.
However, the sums announced on Saturday underline the Gunners' reliance on player sales to help fund squad-building. The figures do not cover this season and therefore do not include any pay-off to former manager Unai Emery, who was sacked in November.
Overall revenue fell from £388.6m to £367.5m. Wages went down from £204.9m to £200.8m.