If you are moving abroad and you have opened an ISA (Individual Savings Account) in the UK, you won't be able to put money into it after the tax year in which you move. Only Crown employees working overseas will be able to deposit money to their ISA while abroad.
You should notify your ISA provider as soon as you stop being a resident of the UK. However, you can still keep your ISA open and get tax relief on money and investments you hold in it. You'll be able to put money again (within the annual ISA allowance), once you have come back and become a UK resident.
Will I be able to use Trading 212's CFD and Invest account?
*If you have moved to the US, and you start paying taxes there, you won't be able to use our services due to the regulations of the Dodd-Frank Act and the FATCA Agreement.
In regards to the rest of the world, you'll be able to use our services and CFD/Invest platform as long as there aren't any local restrictions.