Having brought in Tevez in 2006, the Hammers were fined ?5.5million by the Premier League for breaching the rules governing third-party ownership of players.
However, the Blades suffered relegation that season and, after opening legal proceedings against the Hammers, it was eventually agreed that ?26.5million was owed in compensation.
Sullivan has now revealed that more than ?10million is still to be paid, and the situation is having an impact on Sam Allardyce's transfer plans.
"We've done some good business and brought in some real quality despite our still-limited resources," Sullivan said in the Daily Mirror.
"We have an eight-figure sum still outstanding over the Tevez affair, even though we have been paying it down over the past two years.
"That amount has to be paid off over the next 12 months, which does take its toll on our transfer activity."
