As always, the answer is not a simple yes or no. The way to think of it is if a client is a non-UK relevant individual, no personal pension contribution will be eligible for tax relief in or outside the SIPP. That said, it is possible that limited tax relief is available if your client is a UK relevant individual by virtue of being resident in the UK at some time during the five tax years immediately before the tax year in which they made the contribution, and also resident in the UK when they joined the pension scheme.
Here’s the thing though; working on the basis that the client cannot be defined as a UK relevant individual and is therefore a non-UK relevant individual, personal pension contributions made to a SIPP or SSAS (or other RPS) will not be eligible for any tax relief and do not qualify as a ‘pension input’. Interestingly, since only pension inputs are subject to the Annual Allowance test, such personal contributions, by not being pension inputs, do not use up any available Annual Allowance and are therefore unlimited in terms of the amount the client could pay into the SIPP. This in turn means that no annual allowance tax charge gets triggered by such contributions, regardless of the amount. This is a little-known fact that could stand you in very good stead when dealing with overseas clients who want to pay into a SIPP.