Shares in Net 1 UEPS Technologies plunged on Thursday as investors reacting to a Constitutional Court ruling dumped the volatile stock.

The ruling that the R10 billion social grant tender, previously awarded to Net 1, had to be re-run was the culmination of a nearly two-year legal battle and the beginning of certainty since the disputed contract was allocated to the company in January 2012.

The contract is a major project for the firm, which is has its headquarters in Johannesburg and holds its primary listing in the US.

Shares dropped more than 28 percent to R70 during intraday trading on the Johannesburg Stock Exchange but recovered and closed the session 12.76 percent down to R85.50.

The stock has trailed the FTSE/JSE all share index, declining 8.11 percent for the year to date compared with a 4.2 percent appreciation of the all share in the three months since January.