Switzerland and UK double taxation how does it apply

I am uk passport holder and resident in Switzerland where I am employed with a salary and pay tax. In the uk I have rental income which is split with my partner and this year I have been doing some consultancy work in the uk which is paid into my uk account. I complete the online tax return using an app approved by hmrc. I have three questions as a none resident do I qualify for the the uk tax personal allowance on income earned in the uk? If yes how do I declare this as the app is not applying it when I do the return. (I am resident in Switzerland which is where my family and main income is earned) How is national insurance applied - do I have to pay? Is it possible to not register for VAT if as a one off in future years I earn over 85k GBP in the UK. My consultancy work is will complete next year and I have been told they will pay a completion bonus which brings me over the normal threshold. Thankyou for your assistance

Hi Peter-John Gilbert,

The tax treaty between the UK and Switzerland states that the UK has the right to tax income from UK property.  
This means that you and your partner will each be required to submit a self assessment tax return, in which you declare all of your UK income.  
Any tax that you have to pay in the UK, can be claimed as a credit in Switzerland, as they still retain the right to tax your world-wide income.  
Yes you can claim personal allowances.
Please have a look at the guidance for boxes 15 and 16 of SA109.  (Residence, remittance basis etc notes ).  
UK national insurance is not payable, but as a UK national, you can choose to make NIC payment.  
You will need to contact the NIC helpline for more information.  
Their number is 0300 200 3500 Overseas +44 19 1203 7010 (Monday to Friday: 8am to 6pm Closed on Saturdays, Sundays and Bank Holidays).

You will be required to register in the UK if you make supplies over the threshold of 85K.
However the Place of Supply Rules determine whether you are actually making supplies in the UK and hence whether you are required to register for VAT.
If you are making supplies of consultancy from overseas then this service should come under the General Rule of Services which would mean that your supplies to another business for these services would be accounted for by your business customer under the reverse charge procedure.
This would prevent you from being able to register for VAT in the UK.
Please see the guidance below:
Place of supply of services (VAT Notice 741A) 5. Reverse charge
However please make sure that you belong overseas for these purposes as if you belong in the UK then you would be making UK supplies and hence there would be a requirement to register for VAT.
Please see the guidance below:
Who should register for VAT (VAT Notice 700/1) 9. Non-established-taxable-persons (NETPs) — basic information

Thank you