Fees for those bringing employment tribunal claims have been ruled unlawful, and the government will now have to repay up to £32m to claimants.
The government introduced fees of up to £1,200 in 2013 to reduce the number of malicious and weak cases, but that led to a 79% reduction over three years.
Trade union Unison argued the fees prevented workers accessing justice.
The Ministry of Justice said the government would take immediate steps to stop charging and refund payments.
The Supreme Court ruled the government was acting unlawfully and unconstitutionally when it introduced the fees.