The news comes as the postal operator is slammed by a group of businesses that claim poor service is stifling growth in the online retail sector.
The six-month trial covers consumers living in London and the South East that have bought items from House of Fraser and L’Occitane online. The postal operator adds that it is in talks with other retailers.
Shoppers will be able to request that items are delivered between 6pm and 10pm under the trial, Royal Mail says.
Royal Mail wants to match rivals such as Home Delivery Network, which already offers evening deliveries, and ensure it does not lose revenue from the growing online retail market.
Online sales are forecast to grow to £56bn this year, according to IMRG.
Small and medium businesses have demanded Royal Mail improve the flexibility of their service to boost the sector.
EBay’s online business index has found that 84% of SMEs want the postal operator to improve its services.
They demand Royal Mail improves in five areas including notification of the time or day of delivery as well as evening deliveries.
Royal Mail director Mike Brown says of the trial: “Consumers increasingly want more control over when and where they receive their orders, and Royal Mail is looking to fit the online delivery experience around the shopper, enabling them to select, rather than being told, when their goods will be delivered.”
Ebay surveyed 600 online businesses.