401K tax liability as UK National/Resident (non-US person)

Hi, I have rescinded my US Green card but have 401K which i can withdraw after retirement. I understand US witholds 30% on all withdrawals for NRAs, but due to tax treaty, this is reduce to 15% on 401K, is that correct? Also, will the UK tax anything over and above this or are lump sum withdrawals from US pensions tax free in the UK ? Thank you

Hi ,
 

For current legilsation, There is no legislative definition of a Lump Sum but HMRC regards these as being any non-periodic payment of a pension - That is, any non-regular payment that decreases the value of the remaining pension pot after such payment is made. For example, the first (IRA) withdrawal is taken in year 1, the next withdrawal was made in year 5, and another withdrawal in year 7; such payments will not be regarded as periodic and will be treated as Lump Sum’s under the UK/USA DTA. Whereas any amount withdrawn in set, periodic, frequent intervals (e.g. weekly, monthly, annually etc.) would not be a Lump Sum, but rather periodic payments.   Article 17(2) of the UK/USA DTA provides the US with the right to tax any Lump Sum payment which is made from a US sourced pension scheme (including IRAs). However, the UK is also permitted to tax the same lump sum payment(s), which is in accordance with Article 1(4) of the DTA . Thank you .