How to calculate the threshold for VAT registration?

Dear HMRC I am a locum optometrist and I invoice the various different companies that I have worked for within a few days of the end of every month via my Limited Company. As I am through a Limited Company, I have to use the traditional accrual basis of accounting. The HMRC guidance states: If you exceeded the threshold in the last 12 months: You must register if, by the end of any month, your total VAT taxable turnover for the last 12 months was over £90,000. I am not sure how I should correctly calculate the threshold as this guidance is too vague. Please could you tell me which is the correct method out of techniques 1 to 4 below to calculate my taxable turnover. 1. Do I need to record the date of each day that I have provided a service and each daily invoice amount, and then check the last 12 months of this turnover at the end of every day? 2. Can I to record the date of each day that I have provided a service and each daily invoice amount, and then check the last 12 months of this turnover on the last day of every month? 3. Can I use my accountancy software on the last day of every calendar month to calculate the total 12 months of turnover from the invoices that I have previously submitted? 4. If I use method 3 then can I perform this check on the last day of every calendar month, or must I do this at the on the same day of the end of every month in which my trading year started? i.e. If I started trading on 10th October, must I check my 12 months of turnover on the 9th day of every month? I would prefer to use method 3 as this would be quick, simple and easy, and would reduce the risk of me making calculation mistakes. Please could you let me know if method 3 is an allowable way to calculate my taxable turnover for VAT threshold purposes? Many thanks, 

Name removed admin 

Hi BruceF,
Please see the link below which explains when you would need to register for VAT if you breach the £90K threshold.
3. Working out whether you need to register
The guidance states:
If you make taxable supplies in the UK (read paragraph 2.3), you’re liable to register if:
at the end of any month, the value of your taxable supplies in the previous 12 months or less is over the registration threshold
at any time, you expect the value of your taxable supplies in the next 30 day period alone, to go over the registration threshold
In practice this means calculating your turnover over for the last 12 months from  the last day of the month.
In order to calculate this figure you would need to use the tax points for the supplies you have made over the preceding 12 months.
Please see the guidance on tax points:
14. Time of supply (tax point) rules
Please note that an invoice raised while you are not VAT registered will not constitute a tax point as only a VAT invoice will do this and you can not raise a VAT invoice as a non VAT registered business.
So essentially the tax points of your supplies will be when your service is provided unless a payment is received before the service is supplied in which case the payment date will constitute the tax point.
Thank you. 

Thank you so much for your really detailed reply. This explains everything perfectly! Best wishes, Bruce.