All tours due to depart before 31 August have been cancelled, the operator confirmed late on Thursday (25 June).
Guests can rebook for a future departure, or switch their booking to a different tour.
They can also cancel and rebook for closer to time of departure "for flexibility and peace of mind".
"All travellers booked and fully paid on a tour departing prior to August 31 2020 will receive a 110% credit on tour services, including pre- and post-night accommodation and transfers – excluding airfare and insurance – to be used within the next two years," said G.
"Travellers who haven’t yet made their final payment will have their lifetime deposit kept on file to put towards any tour they choose to take with us in the future.
The operator said Covid-19 was continuing to create "global uncertainty", necessitating its decision to further suspend all tours "for the safety and security of travellers, staff and partners".
G’s terms say requests for cash refunds will be provided "as soon as possible", which is qualified as being "no later than 31 January 2021).
In a statement, G later confirmed: "G Adventures is following guidance from Abta for all UK travellers affected by the tour suspensions.
"All UK travellers booked on a tour departing up to 31 August 2020, who do not wish to rebook their trip to a later date, will receive a fully-protected refund credit note for 100% of the amount paid for all booked tour services, including pre- and post-night accommodation and transfers, as well as an additional 10% travel credit as a gesture of goodwill, to be used on any tour departing up to two years from the end of the month of their tour’s suspension.
"If the traveller desires a cash refund, this will be provided to them as soon as possible, and no later than 31 January 2021, with their money remaining financially protected via their refund credit note in the interim."
