Supermarket giant Tesco withdrew from the Prompt Payment Code (PPC) in June, a week before it was toughened up to require large firms to pay small businesses within 30 days.
More than 3,000 companies are signed up to the PPC. Although it is voluntary, signatories commit to paying their suppliers promptly.
On 1 July, the rules changed to require companies to pay 95% of invoices to small businesses employing under 50 people within 30 days, half the time of the previous 60 days.
Other changes introduced in January mean finance directors or chief executives must take personal responsibility for signing the code, acknowledging that suppliers can charge interest on late invoices and that breaches will be investigated.
According to The Times, Tesco withdrew from the code on 22 June. The supermarket said it did so because it defines supplier size based on the volume of business it does with them, rather than the number of staff, so it isn't practical to commit to the changes.
When the coronavirus pandemic started, Tesco introduced a special payment plan for small suppliers with annual sales under £250,000 and settled invoices as soon as they were cleared. It recently wrote to those businesses saying they will continue to receive payments within five days.
In a statement to the Times, a Tesco spokesperson said:
"We're committed to supporting our smallest suppliers, which is why we’ve recently made permanent the improved payment terms we introduced to help them through the pandemic.