Nigel Farage has been accused of failing to declare financial support from his longtime aide George Cottrell, who was previously convicted of fraud.
According to the allegations, the support included payments for staff, security, and housing before Farage became a member of Parliament. Reform UK denies any breach of the rules.
Farage is also under investigation over an alleged undeclared £5 million gift from crypto billionaire Christopher Harborne.
If Farage is found to have violated parliamentary rules, he could face sanctions, including suspension and a possible by-election.