South Africa's Finance Minister, Pravin Gordhan, has received a summons to appear in court on charges of fraud.
It relates to allegations of misconduct when he was in charge of the country's tax collection service a decade ago.
Mr Gordhan has said the allegations are wholly unfounded and are politically motivated.
The summons requires him to appear in court on 2 November, which is after his budget policy statement due later this month.
The fraud charges relate to alleged severance payments made to two senior executives at the South African Revenue Service (SARS), when it was under Mr Gordhan's leadership 10 years ago.
Prosecutor Shaun Abrahams also told a news conference that Mr Gordhan was being investigated for his role in setting up a surveillance unit at the tax department around the same time.
Mr Gordhan has previously described that allegation as political mischief and has accused the special police unit conducting the investigation, known as the Hawks, of trying to intimidate him.
Mr Abrahams denied there had been any political interference in the matter.
In a statement released later by his lawyers, Mr Gordhan said he was taking legal advice "to bring the matter to an expedited end".
Analysis: Farouk Chothia, BBC News
South Africa's finance ministry once had a reputation for being immune from corruption, and the political shenanigans in the governing African National Congress (ANC).
But that changed last year when South Africa had three finance ministers in a week.
Analysts saw President Jacob's Zuma attempt to install David van Rooyen - a political lightweight - as finance minister in December as a power grab by an elite perceived to be corrupt. They were defeated, with Mr Zuma forced to appoint Pravin Gordhan.
The new minister warned of South Africa turning into a kleptocracy, and pointedly distanced himself from Mr Zuma's business allies.
But now Mr Gordhan faces a charge of fraud - and the courts will decide whether he was masquerading as a champion of good governance or, as he claims, is the victim of political mischief.
He will probably become the first government minister in South Africa to be tried while in office - unless Mr Zuma fires him before then.
Either way, it sets the scene for more political and financial turmoil in a country which was a beacon of hope for all of Africa when Nelson Mandela became its first black president in 1994, ending white-minority rule.
Mr Gordhan's efforts to rein in government spending have won him respect in the financial markets.
News of his summons rattled the markets and the South African rand fell more than 3%.
When President Zuma sacked Nhlanhla Nene as finance minister in December replacing him with David van Rooyen, the widely-criticised move sent the rand to record lows and caused the stock market to tumble.
Within a few days Mr Gordhan was appointed in Mr van Rooyen's place - a move designed to quell market discontent and restore some confidence.
Many analysts believe that President Jacob Zuma would like to replace Mr Gordhan, who had previously served as South Africa's finance minister from 2009 until 2014.