Three quarters had still done nothing to prepare and a third of respondents said they were just "hoping for the best".
The study, carried out by the chartered accountancy firm HW Fisher & Company, found "worrying" levels of confusion and complacency among small business owners about their imminent requirement to start a workplace pension.
Even though 1.3 million SMEs will have to offer a pension scheme to their staff during the next four years, the survey of small companies found that two thirds (67%) of respondents had no idea of the 'staging date' when they must comply.
Nearly a third (32%) felt they didn't know enough about auto enrolment to be able to gauge its likely impact on their business, and almost half (49%) said they understood little or nothing about the changes they will need to make.
Even more striking was the way respondents were preparing – or rather, not preparing – for the arrival of auto enrolment.

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Fewer than one in four (23%) had taken steps to get ready, with nearly twice as many (42%) saying they know what needs to be done but have yet to start. Some 35% admitted they had done nothing as they don't know how to start.
In total three quarters (77%) had still not begun to get ready for the changes.
Those polled gave a bleak assessment of their preparedness for the arrival of auto enrolment.
Half (52%) described themselves as "not at all ready", with a mere 21% declaring themselves "completely ready".
Yet despite this lack of preparation, there was complacency. Some 34% of respondents said they were still "hoping for the best", with a further 24% feeling "completely confident".
Sailesh Mehta, partner at HW Fisher & Company, said: "So far auto enrolment has only affected Britain's larger firms, but for the army of small business owners it is just around the corner.
"So it's worrying that so many of them are burying their heads in the sand – auto enrolment is coming for everyone, and if you run a business, it's coming for you.
"From August firms with more than 60 PAYE employees will have to comply, and by this time next year thousands of firms with fewer than 30 staff will have to offer their employees a pension.
"The smaller the company, the later the staging date – but this is no reason to ignore your obligations. The earlier you start to prepare for auto enrolment, the easier the transition will be."