The extent of debts at the main trading companies, Twenty 1 Construction and Twenty 1 Interiors, has been exposed in a report from administrator Grant Thornton.
Trade creditors were warned that HMRC, preferred creditor, was owed £9.7m, meaning there would be no funds available to pay them.
In retentions alone £3.3m was held by Twenty 1 Construction and will be lost.
Twenty 1 Group navigated the pandemic down during most of 2020 and 2021 with assistance of a £2m coronavirus large business interruption loan facility with HSBC as well as deferred payment terms from HMRC.
But as collecting client payments became increasingly challenging, deepening cashflow problems saw the directors call in Grant Thornton to explore selling the business but no buyer was found.
When the administrators were called in Twenty 1 Construction was owed around £6m by clients but to date just £410,000 has been collected.
Twenty 1 Construction was set up just over 10 years ago by fit-out industry veterans Keith Ashcroft and Paul Gaughan.
Ashcroft had previously worked at John Doyle group-owned Ibex Interiors as a construction director for 15 years, while Gaughan had previously worked for Byrne Group-owned fit-out arm Chorus for six years and before that he also worked at Ibex.
Twenty 1 Construction grew steadily from around £13m turnover in 2015 to around £68m in most recent published accounts for 2020.
Around a third of revenue was generated on complex refurbishment jobs and the rest from commercial fit-out work with an expertise in occupied premises projects.
Around 64 staff lost their jobs when administrators were appointed on 21 March.