Hi,
Residence in the UK is primarily based on the number of days you are physically in the UK. You would need to undertake the statutory residence tests. after reading the guidance at RDR3, to determine your residence position.
RDR3 Statutory Residence Test
If you are not tax resident in the UK for the whole tax year, then you would only declare in the UK, any UK income or capital gains that arise. For example, bank or buiding society interest, UK dividends and UK capital gains. Any income or capital gains, arising outside of the UK, will not be taxable in the UK. They may be taxable in other countries.
In order to use the remittance basis, you are required to be resident in the UK for tax purposes. The remittance basis does not include National Insurance. That is a separate matter to Income Tax.
You can pay up to 100% of your earnings in a tax year, up to the maximum of your employment income or £60000, whichever is lower in the tax year you leave the UK and £3600 each year for the next 5 years, provided there is an existing UK pension scheme.
You cannot contribute to an ISA scheme in any tax years that you are not UK resident. You can in the tax years you leave or arrive in the UK.
We cannot comment of future tax years, as guidance may change.
Thank you.