The issuing of post-dated cheques for current debt is one of the classic signs of insolvency.
Solvent debtors very rarely, if ever, issue post-dated cheques as they immediately raise the suspicion of insolvency. A debtor who has a long-term history of issuing post-dated cheques is almost certainly insolvent.
Cheques that bounce may also be an indicator of insolvency but again they might just simply be an indicator of a short-term cashflow problem.
