The National Union of Students is facing a shortfall of £200,000 and has been forced to cut back its spending.
A change in the union's tax status, prohibiting it from reclaiming VAT, will cost it £100,000, while cuts to its members' block grants - which come from the universities - mean it will lose another £100,000 in affiliation fees.
NUS president Owain James said plans were in place to claw back £140,000. He said: "We are finding a balanced budget."
Unions that are not "active" - that do not attend NUS conference, for example - might be asked whether they want to stop receiving mailings.
Some students are protesting against this move. One group has launched a "Save Our Union" campaign. It claims that the cuts will "set in motion a vicious circle that will see many further education and smaller higher education unions disenfranchised and the NUS financially ruined".
Mr James said the move would not disenfranchise unions because they would be frequently consulted about receiving campaign materials.
The budget shortfall might also lead to cuts in staff levels at NUS headquarters. Talks have been initiated with trade unions.
South Bank University has slashed its student union's grant as part of an action plan to deal with financial woes. Sabbatical officer Ilana Fox said:
"We are dealing with it as best we can by reducing some levels of services."