Glenda Ivy Burgess is standing trial in the District Court charged with 18 counts of aggravated deception

A former account manager at one of the state’s largest companies is standing trial over an alleged multimillion deception, but prosecutors don’t know why, a court has heard.

A senior account manager is standing trial charged with deceiving her former employer out of millions of dollars, but prosecutors cannot say why, a court has heard.

Former Adelaide Brighton Cement accounts worker Glenda Ivy Burgess allegedly falsified company accounts, by hiding the debt of a customer, Concrete Supply.

The 63-year-old from Hillbank is standing trial in the District Court, after pleading not guilty to 18 counts of aggravated deception.

Opening the trial on Wednesday, Peter Longson, prosecuting, told the jury the cement and lime business “became aware of some unusual errors in accounting systems” which favoured Concrete Supply.

“Between August 1, 2009 and September 30, 2017, Concrete Supply had received in excess of $32m worth of product … but they had only paid a little over $20m.”

He said Ms Burgess was responsible for a team of three other people who sent out automatically generated invoices and manually allocated payments received. They were also responsible for chasing up bad debts.

He said another, interstate, manager of Adelaide Brighton Cement “noticed that there were some large entries” of over $100,000 that were manual entries.

The jury heard those entries related to money from other customers were applied to the Concrete Supply account, reducing their debt by $3m.

Other manual entries involved debts from the Concrete Supply account being manually allocated to another customer’s account. He said these entries amounted to about $5m.

Mr Longson told the jury these manual transactions occurred under the username “Glenda B”, which belonged to Ms Burgess.

Former Adelaide Brighton Cement accounts worker Glenda Ivy Burgess allegedly falsified company accounts, by hiding the debt of a customer, Concrete Supply. Picture: NCA NewsWire / Naomi Jellicoe

He told the jury she was also required to prepare a monthly report of the customers with the top 10 debt amounts, a list which later expanded to the top 25. He said Concrete Supply should have been on that list each month over the eight-year period, but only appeared once.

Ms Burgess also allegedly twice increased the credit limit for Concrete Supply without approval, raising it from $400,000 in 2010 to $1.5m. In 2014, she also allegedly increased the limit to $3m.

Mr Longson said Concrete Supply stopped receiving invoices in about 2012 and stopped receiving statements in 2013.

He said they used delivery dockets to create their own invoices and sent a cheque, and had an understanding they were entitled to a rebate of about 30 per cent.

Mr Longson said it was not possible to say why Ms Burgess allegedly deceived her employer.

“Why the defendant has taken these steps to transfer debt, to allocate other customers money to Concrete Supply, to raise Concrete Supply’s credit limit … the prosecution can’t say.

“Police have conducted inquiries. They don’t show any contact between the defendant and the people of Concrete Supply.”

He said she was not living beyond her means, and no large deposits of money were detected in her bank accounts.

“As unsatisfactory as this might sound … the prosecution is not required to prove why a particular person committed a crime,” he said.

Instead, he told the jury the prosecution were only required to prove the defendant did what was alleged.

“Why she did it, we won’t be able to tell you.”

The trial, before a jury of eight women and four men, continues.