“LEGACY issues” with the council’s 2018/19 accounts will be the “most challenging” for auditors to investigate.

Last month, Slough Borough Council announced it has corrected and refiled its 2018/19 accounts after external auditors Grant Thornton refused to sign off its books and added four statutory requirements the council to undertake after it found numerous ‘inadequacies’.

They found the local authority’s finance team had ‘insufficient skills or capacity’ to produce statements or working papers of quality and had ‘inadequate’ governance arrangements over its subsidiary and joint venture companies.

After further digging by the council’s interim finance team, they found Slough clocked up £760m in borrowing debt and a £479m blackhole, forcing the council to declare bankruptcy and be under government supervision.

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The council said the corrected 2018/19 accounts are “radically different” and hopes when it is signed off, it will give ministers confidence in its financial position.

Speaking at an audit and governance committee on July 28, external auditor Julie Masci said: “The 2018/19 process will probably be the longest one of the ones we need to do to catch up because of the legacy issues that we need to understand and get comfortable with.

“That gives the council a good baseline in terms of once they have that assurance over that set of accounts, the subsequent years will get easier.

“But the 2018/19 accounts are the ones that will be the most challenging.”

She also said it’s “very early days” within Grant Thornton’s inspection into the revised 2018/19 accounts but will bring a report to the next committee where they would have progressed “significantly”.

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Chief finance officer Steven Mair said they hope the inspection will conclude by the end of September but warned that won’t be the end of the line for the 2018/19 accounts given the huge scrutiny Slough is under.

He explained: “Colleagues in external audit will likewise be subject to a number of reviews, partner reviews, technical reviews, and possibly a review under an organisation called Public Sector Audit Appointments simply because of the lateness of the accounts.

“All of those reviews could take us until December before you get a final signed off, completed, fully finished set of accounts.”

The council expects to complete 2019/20 accounts for inspection by the end of September, the 2020/21 by the end of the year and 2021/22’s by March 31 2023.