Hartlepool chairman Ken Hodcroft says manager Danny Wilson must trim his squad if he wants to sign new players.
Football League rules mean salaries must not exceed 60% of League Two clubs' turnover, so Hartlepool must tighten their belts after relegation.
Wilson has already had to let several key players leave Victoria Park.
"From 15 July we are unable to buy or bring in on loan any players until we reach that requirement," Hodcroft revealed in the club programme.
"The departures of Chris Llewellyn, Thomas Butler and Adam Boyd and the loan of Darrell Clarke to Rochdale helps us move towards it.
"However, it also depends on revenue and we receive considerably less from the Football League in this division so we need your (fans') support through the turnstiles."
Since Pools were relegated in May, Llewellyn has returned to Wrexham, Butler has joined Swansea and Boyd was sold to Luton for £500,000, while Clarke has joined League Two rivals Rochdale on loan.