Severe disruption caused by major engineering work at the UK's busiest station will have "lasting implications" for small businesses, a trade body has warned.
Nearly half of London Waterloo's platforms have been closed until August 28 to enable the project, including extending platforms, to take place.
Commuters from areas such as Woking, Guildford and Surbiton have been warned the South West Trains timetable will be significantly reduced.
And employers and small enterprises in the area will likely face unforeseen losses such as cancelled bookings, the Federation of Small Businesses said.
Sue Terpilowski, the FSB London policy chairwoman, said: "Whilst our members will be doing everything they can to work flexibly around the disruption to rail services at Waterloo and other mainline stations across London this month, there will be lasting implications for small businesses already on tight margins.
"This is peak season for tourism and for those businesses in the hospitality or retail sectors the impact will be felt more keenly. Many restaurants, hotels and shops will experience cancelled bookings and lost sales that will not be recovered when the work at the stations is completed.
"Some small businesses are able to allow staff to work at home, but many cannot. Whatever approach they take, will cost time and money to arrange, which at a time when the cost of doing business in the capital is rising, they can ill afford."
Colin Stanbridge, chief executive of London Chamber of Commerce and Industry, said his members backed the aim of the project but questioned whether the level of disruption was "really necessary".
And he said: "While Network Rail are advising people to work from home, take leave around this period or avoid peak hours, this is not always possible or practical.
"Staff often have to be in the office to do their job, to have the required level of input in meetings and for many roles in service provision such as restaurant staff it is literally impossible to do their job away from their place of work or work alternative hours."