Hi anna11111,
If you are providing consultancy services to an overseas client then this will Outside The Scope of UK VAT and will not go towards your taxable turnover for VAT registration purposes.
You can choose to register voluntarily but once registered you would not need to inform us that you are not charging VAT and you would just declare the VAT on yout outputs as nil.
Please see the guidance at:
Who should register for VAT (VAT Notice 700/1) and specifically section 2.9.
Thank you