Tax return issue: not sure how to describe myself

I run a limited company and am the sole director and shareholder. I believe that tax should be payable on the amount of dividends received, less an allowance of £1k for the last tax year, plus £12,250 or thereabouts as my personal allowance, so I had it worked out to be roughly £5k to pay. When I tried to file online, it came up with a bill of £12k. It asked me for the name of the company, but I then had to delete that as it was asking for PAYE details which I don't have; I don't pay myself a salary, only dividends. Could someone please walk me through what I should be doing here please? Thanks in advance.

Hi,

To advise you correctly regarding your calculation, we may need some more information. Please contact our Self Assessment team for advice.

Self Assessment: general enquiries

Thank you.