Spurs earned £690m worth of income last year, according to data from the Uefa European club finance and investment landscape report, putting them ninth overall in Europe.
That income would take a serious hit if they were to drop into the Championship.
According to BBC Sport analysis, the reduction could be as much as £261m overall.
One key area in which they would be harmed is ticket revenue, which earned the club £130m, the fifth-highest across the continent.
Currently, Spurs charge an average of £76 per fan for each home match, with only five clubs in Europe costing more.
Since building their new stadium for around £1bn, Spurs have focused heavily on selling hospitality tickets and corporate packages for matches in order to maximise matchday takings.
But they will simply not be able to charge the same amount for an opening day fixture against a side like Lincoln City – who are currently chasing promotion from League One – in the second tier in August, should they ultimately finish in the bottom three, and a drop in attendances would likely occur too.
Elsewhere, Spurs’ broadcast revenue would plummet too. They would no longer have access to the funds generated from the Premier League’s lucrative domestic and international broadcast deals, which last year meant Ipswich Town earned more in broadcast revenue than Barcelona.
And the tens of millions they earn from Champions League TV income will drop to nothing, unless they manage to win the tournament, which would guarantee them a place in next year’s competition even if they are playing second-tier football.
Furthermore, the club-record £269m of commercial income Spurs earned last year would likely take significant damage.
Sponsorships such as kit manufacturer Nike and front-of-shirt sponsors AIA’s deals (worth around £70m combined annually) will have their values slashed thanks to relegation clauses.
Playing four more home matches in the Championship could also have an impact on Spurs’ ability to host other lucrative events and concerts, which the club has heavily focused on.
“For a club of Spurs’ ambitions and financial scale, relegation would not simply be a short-term sporting setback”, says football finance expert Kieran Maguire. “The economics of English football make recovery a multi-year project.”