B&M European Value Retail SA 's finance chief has stepped down, the chain said on Monday, after it discovered £7m of costs had not been correctly recognised, hitting profits.
In a brief update, the bargain chain said the overseas freight costs had not been recognised in costs of goods sold, following an operating system update earlier this year.
The underlying issue has since been resolved, it confirmed, but not before hitting profits.
As a result, it cut forecasts for the second time this month.
Full-year earnings are now expected to come in between £470m and £520m, based on revised second-quarter margin run rates. It had previously predicted adjusted earnings before interest, tax, depreciation and amortisation of between £510m and £560m for the 2026 full year.
Interim adjusted EBITDA, meanwhile, was slated to come in around £191m, compared to previous guidance of £198m.
Shares in the FTSE 250 group plunged earlier this month after it revealed earnings had been hit by sliding UK sales and soaring costs, prompting it to slash guidance for both the full and half year.
B&M, which has more than 1,100 UK stores, also confirmed that chief financial officer Mike Schmidt has resigned.
"A search for his successor has commenced and Mike Schmidt will remain with the company until a replacement is in place to ensure an orderly transition," it said. "The board wishes Mike well for the future."
Schmidt jointed B&M in 2022 from DFS, where he was group financial officer. He was briefly interim chief executive earlier this year, following the retirement of Alex Russo. Veteran retailer Tjeerd Jegen took on the role on a permanent basis in June.
Half-year numbers are due out on 13 November.