Pretoria - Former Sars employees Ivan Pillay and Johann Van Loggerenberg were greeted by supporters as they arrived at the Hawks offices in Pretoria on Thursday.
Civil society groups Right2Know, Section27 and Corruption Watch have all pledged solidarity with them.
Among the supporters present were Advocate George Bizos, Francis Antonie from the Helen Suzman Foundation and former judge Johan Kriegler from Freedom Under Law.
The crowd was singing and dancing while waiting for feedback from those inside.
Activist Mark Heywood said the day was a defining moment for the country as those summoned were facing fabricated charges.
"The charges are part of a political vendetta against people in the government that are fighting corruption. We are here as civil society organisations and we want to see what is going," said Heywood.
Ronald Menoe from Corruption Watch said they wanted to understand what is happening.
"We are worried about the timing of all of this," he said.
On Thursday, the spotlight will be on the rand and the Directorate for Priority Crimes, otherwise known as the Hawks after the bombshell announcement that the Minister of Finance, Pravin Gordhan, has been summoned for the first stages of possible criminal charges.
Gordhan was supposed to present himself to the offices in Pretoria on Thursday to receive a warning letter - usually a precursor to charges - but said he would not be going, on the advice of his lawyer.
After saying he just wanted to get on with his job, he went on to deliver an overview of the local and global economy to a business gathering in Cape Town.
The Economic Freedom Fighters have urged Gordhan to change his mind and keep his 14:00 appointment, out of respect for the institutions of state, even though it believes he is innocent.
The furore relates to an investigation by the Hawks into the alleged establishment of intelligence capacity in Sars; the recruitment of investigators to work for this unit, and “Project Sunday Evenings”. The latter was an allegedly illegal Sars operation to record conversations of members of the now-defunct Scorpions unit.
It was not clear what the Hawks would allege Gordhan’s role or knowledge of these matters was.
In the meantime, Civil society organisations are expected to wait outside the Hawks' offices to get first hand information of what the charges against Gordhan and his former colleagues are, and what the Hawks' intentions are.
Former SARS deputy head Pillay and investigative unit head Van Loggerenberg are expected to be the first to go in on Thursday morning.
According to a News24 report on Thursday night, Gordhan is alleged to have to have let Pillay go on early retirement, and then be rehired on a contract. Van Loggerenberg headed a controversial unit within SARS that conducted special investigations.
The issues have has dogged Gordhan since he was reappointed as Finance Minister after President Jacob Zuma suddenly removed Nhlanhla Nene last December. Nene was replaced by David Van Rooyen and amid an uproar was quickly removed to the Department of Co-operative Governance and Traditional Affairs and Gordhan was returned to the position.
Hardly settled back in to the job Gordhan was sent a list of 27 questions by the Hawks.
In a statement on Wednesday, Gordhan said he had answered all of their questions, and had been advised by his legal counsel that he did not have to present himself to the Hawks, adding that the claims against him were unfounded.
And amid the uncertainty, the rand took a tumble.
Fin24 report that by late Wednesday afternoon the currency was down 4.91% at R14.24 to the dollar, down 4.23% at R16.02 to the euro and down 5.63% at R18.84 to the pound.