Thousands of Tesco staff following the scheme have saved between £5 and £50 every month during a three or five year period.
When the scheme matures those staff will be given the option to buy Tesco shares at the price set when they joined.
Tesco shares cost 305 pence in early afternoon trade on Monday.
And employees who started the scheme five years ago can now buy shares at the 1999 option price of 151 pence each, while those who joined the scheme three years ago can buy shares at the 2001 price of 198 pence.
Therefore, staff who invested in the Save As Your Earn (SAYE) plan in 1999 will make a profit of up to £3,929 each.
Staff can either sell their new shares or retain them as a long-term investment.
Tesco said over 74 per cent of staff have chosen to keep their shares. More than 100,000 of the Tesco's 237,000 employees hold shares in the company.
"Being a shareholder in Tesco is important to so many of our staff because it gives them a personal stake in the company's success," said Tesco chief executive Sir Terry Leahy.
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