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In regions where the development of formal finance is relatively lagging behind, commercial credit has partially replaced the role of formal finance and facilitated the development of the private economy and even the country, thus making commercial credit an important entry point for understanding and promoting sustainable economic development. Taking the Hangzhou Bay Greater Bay Area as a case study, based on the City Business Credit Environment Index (CEI) from 2015 to 2019, we examine the characteristics of business credit networks using social network analysis and discuss the impact of business credit on urban green economy efficiency heterogeneity by drawing on spatial econometrics. The study confirms that the structure of business credit networks in the Hangzhou Bay Greater Bay Area tends to be dense, the network density and number of connections show growth, the spatial network structure is taking shape, and the strength of spatial connections among cities has increased. Hangzhou, Shaoxing, Jiaxing and Shanghai are at the centre of the network and play a radiation-driven role. The business credit network in the Hangzhou Bay Greater Bay Area is characterised by self-stability and has evolved from a multi-centre to a single centre. Business credit is negatively correlated with the efficiency of the green economy in the Hangzhou Bay Area, which is a departure from the Chinese "financial development paradox". In terms of heterogeneity, the relationship remains consistent for port cities and open coastal cities in general, while the effect is less pronounced for cities above sub-provincial level. The study concludes that, with the high-quality economic development of the Hangzhou Bay Greater Bay Area, the Chinese "financial development paradox" does not exist in the region at this stage, which also highlights the need to accelerate the construction of a Chinese-style modernisation theory and practice system.