I was wondering, if a Tax Invoice does not meet the SARS minimum requirements. Is that debt then still payable?

Here is the picture:
Service was rendered on 2020/09/25 for R15,000.00, therefore it is not returnable.
Tax Invoice was issued 2020/10/10 which is within the 21 days allowed to issue said invoice
However the invoice does not meet all the other requirements as specified in the VAT act.
Now it is 2020/10/30 meaning the invoice can be fixed, however the new fixed invoice would be outside the 21 days allowed to deliver the Tax Invoice

Would an invoice which does not meet the requirements in the VAT act be an illegal document?
Would an illegal document be the same as an illegal act or trade?
Is the debt still payable, or is it void?