The Financial Reporting Council (FRC) has sanctioned PriceWaterhouseCoopers (PwC) and audit partner Steve Denison in relation to the 2014 audits of BHS and the Taveta Group (Taveta).
PwC and Steve Denison have admitted Misconduct and accepted substantial fines and non-financial sanctions.
PwC said there were “serious shortcomings with this audit work”.
The collapse of BHS in April 2016 led to the loss of 11,000 jobs and a pension deficit of £571m.
The regulator fined PwC £10m, reduced to £6.5m for early settlement.
Partner Steve Dennison was fined £500,000, reduced to £325,000 for settling early.
Mr Denison will also be struck from a register of auditors and cannot reapply to be reinstated for 15 years, effectively ending his career.
PwC said: “We are sorry that our work fell well below the professional standards expected of us and that we demand of ourselves.”
“At its core this is not a failure in our audit methodology, the methodology simply was not followed.”
It said that the audit failings “did not contribute to the collapse of BHS over one year later”.
PwC added that it had overhauled its monitoring procedures.
Mr Denison left the audit firm this month after nearly 33 years there following the FRC ruling.