The firm now has until the end of April before tests take place, as discussions with stakeholders on the reduction of net debt are expected to last until the first quarter of 2018.
Carillion's interim chief executive Keith Cochrane said: "We believe that our lenders' decision to defer the test date demonstrates their continuing support. We remain focused on actively progressing a constructive dialogue with our financial stakeholders on the group's recapitalization plans."
The group warned in November that it might breach its financial covenants by the end of the year, with potential delays affecting PPP disposals.
Meanwhile, Carillion’s new CEO Andrew Davies is to start on January 22, effectively replacing interim CEO Keith Cochrane.