WA Workcover WA requests information then sends me an infringement based on what I told them

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20 June 2017
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I'm hoping someone can help me who's one, it has me quite worried.
So I run a small business and have a few workers. I changed my address and my workers comp expired for 4 months until I got a new policy.
Out of the blue I get this official looking letter saying I need to give them info or I would be penalised for not cooperating. The letter makes it sound like if I fill out the form nothing else would happen.
It asked for worker