Surging stock transaction volumes pushed up stamp duty revenue on stock trading in the first half of the year to an estimated record 138 billion yuan ($22.26 billion), the highest six-month figure on record and a rise of 545 percent year-on-year, according to data of financial information provider Shanghai Wind Information Co Ltd.

Stock trading stamp duty is 0.1 percent of the transaction value, and is only imposed on sellers.

The tax on stock trading is among China's fastest-growing fiscal revenue category, although it only accounts for 2 percent of its total 6.65 trillion yuan in government revenue in the period, Economic Information Daily reported.

Market insiders said the fluctuating A-share market in the first half of the year spurred transaction volumes, pushing up the daily turnover rate.

"Rising stamp duty reflects how active the stock market has been in the first half. Last year at this time, the turnover rate was relatively low and transaction volume smaller," said Xia Yiheng from Aijian Securities Co Ltd.

Some experts have said they were advising a cut or even suspension in stamp duty on stock trading in late June, amid the A-share turmoil as a measure to boost market confidence.

Besides its function as an important source of national revenue, stamp duty may also affect investor sentiment, reported the newspaper, citing Zhang Bin, an economic strategy researcher with the Chinese Academy of Social Sciences, and any adjustment in the duty may also be interpreted as interference in the market.