Small and medium enterprises (SMEs) are losing £1,277 each on average because of inaccurate accounts calculations, according to the Association of Accounting Technicians (AAT).

The group’s research of growing businesses found that more than a third use under-qualified finance staff, resulting in mistakes and paying too much tax.

It says the average figure is composed of £508 in tax mistakes, £399 in unissued invoices and £257 in bounced cheques that are not chased up.

Rounding the figures up, the problem could be costing UK SMEs about £2.9 billion a year, said the AAT.

It’s common for people working in small businesses to be responsible for more than role. Sole traders, meanwhile, have to do everything from the accounts to the tea.

The AAT calls this a “silent risk” to the UK’s small businesses.

Mark Farrar, chief executive of AAT, said: “Running a small business always involves juggling a lot of different priorities.

“With so much to think about, investing in a qualified member of staff to look after finance and accounting is often seen as a big step.

“What’s worrying is that many business owners think that finance and accounting for their business isn’t complex enough to need a qualification, and that whoever looks after it can just learn on the job.

“The fact that businesses are losing money through accounting mistakes shows that this isn’t the case. Small businesses are often fragile, especially in their first few years, and every pound matters.”

In other findings from the research, six in 10 staff in charge of finances perform another role for the business, with half also doing business development and sales.

The research also revealed a lack of proper training in some firms, with 15% admitting they had never invested in courses and 26% saying they had no dedicated training budget.