Eighteen charges of non-declaration of assets against Saraki, the head of Nigeria's senate, were dismissed after almost two years of legal wrangling.
Buhari has been in London for almost a month, sparking rumors about his health.
Nigeria has recovered more than $500 million in cash and has seized over $9 billion in assets.
At least five people were killed in Nigeria's Enugu state in the latest clashes between herdsmen and farmers.
The Nigerian commodities billionaire has been linked to at least four offshore shell companies.
After allegations of corruption and copies disappearing, Nigeria's budget fiasco goes on.
Allegations against Saraki include that he acquired wealth beyond his legitimate earnings.