This hidden build-up of substandard corporate loans, spurred by China’s slowest economic growth in 25 years, flatters the strength of its banks’ balance sheets and would hit earnings if the loans were declared in default and written down.

“In the past, NPLs outnumbered overdue loans,” said an official at the China Banking Regulatory Commission, who spoke on condition of anonymity. “Now overdue loans are surpassing NPLs.”

At 18 listed Chinese banks, overdue loans that had not been written down jumped 57 per cent to 645 billion yuan in the first half of this year from the end of last year, while NPLs increased 17 per cent to 692 billion yuan, a UBS analysis of Chinese banks’ balance sheet data shows.

For loans overdue for more than three months, the increase was a hefty 166 per cent to 149 billion yuan, a problem that analysts say is more widespread at mid-tier and smaller unlisted Chinese banks.

“Downward pressure” in the economy was causing Chinese banks to classify loans more flexibly to avoid having to increase the amount of capital they set aside for loan defaults, the CBRC official said.

“The true asset quality of Chinese banks is worse than what appears in the reported NPLs,” said Ritesh Maheshwari, a bank analyst with Standard & Poor’s in Singapore.

Recognising loan losses was not an issue among Chinese banks before 2012, when the volume of loans categorised as overdue but unimpaired was negligible.

As growth slowed, however, lenders have grown wary of fully declaring bad debt, senior bankers and industry players said.

If they do declare a lender as delinquent, it would have a domino effect, since the information is posted on the central bank’s national credit database, prompting all banks to write down their loans to the same borrower.

Bankers are reluctant to take such a hit to profit if they believe the loan can eventually be recovered, in full or part.

“If an overdue loan is classified as entirely non-performing, then we have to set aside 100 per cent in provisions,” said a senior executive at a joint-stock Chinese bank. “But we may not have 100 per cent of loss. So it’s not reasonable to put aside so much. It’s a waste of capital.”

In September, rating agency Moody’s started calculating new overdue loans for 90 days or more to better assess asset quality at Chinese banks, since they believed NPLs did not give a full picture, said Christine Kuo, a senior Moody’s analyst.

At Shanghai Pudong Development Bank, loans delinquent for more than 90 days but not written down doubled in the six months to June to 22.96 billion yuan.

Hua Xia Bank, Ping An Bank, Industrial Bank and China Minsheng Bank also reported a significant rise in overdue loans in the first half of this year.

The big state-owned commercial banks, led by Industrial and Commercial Bank of China, are more diligent about recognising their asset quality, bankers and auditors said.

More than 99 per cent of loans that have missed a payment for more than three months were classed as non-performing, an ICBC executive told analysts last month on the bank’s third-quarter earnings call.

But at several mid-tier banks, provisions for possible loan losses are seldom matching growth in the overdue loan book, pointing to a potential capital shortfall.

At Bank of Chongqing, for example, long-date overdue loans more than doubled in the first half, while provisions only increased by about 10 per cent.

“There’s a risk that provisioning coverage will be insufficient,” said Grace Wu, head of China bank ratingsat Fitch.