Participants will receive mentoring and networking opportunities.
PayPal and Braintree have added three start-ups to their Start Tank programme.
AudioTribe, Mihaibao and Zipcube will receive benefits including access to mentoring and thought-leadership from the two companies, plus networking opportunities with angel investors and venture capitalists, working towards a demo day where they will present their vision and business models.
They will also gain access to benefits such as waived PayPal and Braintree fees and a dedicated customer care team.
AudioTribe is a platform connecting unsigned musicians with relevant contacts in the music industry, while Mihaibao provides Chinese customers with easy cross-border online shopping, combining many stores into a single checkout. Zipcube, meanwhile, is an online marketplace for meeting rooms, desks and venues.
The companies join current programme participants Henchman, Localz and MegaTransfert on the programme.
PayPal and Braintree Developer Senior Director, John Lunn, said: "These are all interesting companies joining us who I believe have an exciting future ahead of them. I am confident the Start Tank programme will support them as they work to achieve their goals and give them the start they need and deserve."
Start Tank was launched in the UK in July 2014, having previously been rolled out in Boston.