The capital is to be used by the Lye-based manufacturer of industrial labels, electronic components, screen-printed and digitally printed labels and graphics to fund the acquisition of Oxford Padprint Techniques.
It is claimed to be the first peer-to-peer loan used to fund a corporate acquisition.
Customark was established more than 40 years ago and employs 44 staff in its two offices in the West Midlands and Wiltshire.
Customark managing director Greg Lerigo said: "We wanted to buy Oxford Padprint Techniques outright and fund it primarily using cashflow from the business.
"Unfortunately, the banks aren't keen to lend this kind of capital, preferring to fund much larger acquisitions. It's only thanks to ThinCats' flexibility and dedication to understanding our objectives that we were able to complete the deal and continue our acquisition-led growth strategy."
Launched in January 2011, Staffordshire-based ThinCats is an online marketplace allowing investors to make secured loans directly to UK businesses. It has assisted with 20 loans to 12 businesses, totalling more than £2.6m.
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