However, boss Simon Cooper said the group remained well-positioned to ride out the Covid storm, to "capitalise on inevitable structural change in the market" and to "look to the future with confidence".
The group on Thursday (10 December) posted a pre-tax loss of £46.3 million, which includes £41.7 million attributed to the "cost of Covid-19".
It said the loss owed to a "significant reduction in new bookings", cancellations and associated administrative costs.
Total cash, though, as of 30 September was £36.5 million, excluding customer cash of £25.8 million held in trust.
This total cash position has since increased to £51 million as of 30 November, the group revealed in its full-year results statement.
It is also yet to draw from a £75 million revolving credit facility arranged in May.
In the event of a period of zero revenue, the group estimates monthly cash burn of around £2 million.
As of 30 November, On the Beach had paid £165 million in refunds since 15 March; refunds for hotels and transfers have so far amounted to £72 million, and flights £93 million.
While it awaits a final £4 million owed by airlines, the group has refunded flight costs in advance "to protect the brand and generate customer goodwill".
"There continue to be substantial delays receiving refunds from airlines," said On the Beach. "The group continues to pursue these rightful refund claims on behalf of customers.
"In many cases, we have refunded customers in advance of receiving the flight monies from airlines."
Looking ahead, On the Beach said booking volumes in October and November were "significantly below normal levels" with consumer holiday appetite remaining "subdued".
Factors suppressing demand, it said, includes "regularly changing" Foreign Office advice, "onerous" entry requirements in-destination, and return quarantine requirements.
It further stressed the timing of peak booking demand, typically in January, in full-year 2021 (year to 30 September 2021) would be "significantly influenced" by the progress of the pandemic, and the policy response of the UK government and those in the EU.
The group declined to offer any guidance for full-year 2021. A further update will be provided at its AGM on 5 February next year.
On the Beach chief executive Simon Cooper said: “There is no doubt that 2020 has significantly impacted the entire global travel industry and that the effects of the pandemic will have lasting impacts on the way the industry conducts business for many years to come.
“On the Beach continues to successfully build a leading position as more consumers discover the ease of use and vast choice of beach holidays across our platforms.
"The flexibility and asset-light nature of our business model, together with our recently strengthened balance sheet and the actions we have taken since the middle of March, means we are well placed to capitalise on the inevitable structural changes in the market post Covid-19.
"As a result, the board continues to look to the future with confidence.”
