https://help.gosimpletax.com/hc/en-gb/articles/360000808610-Pension-Savings-Tax-Charges
Box 11.1 SA101 Ai4
This is for UK Registered Pension Schemes.
Your pension scheme administrator should have given you the information you need to fill in this box
On the Pensions and Benefits Page, Click on + INCOME
Select the income category: Pension Benefits transferred subject to the overseas transfer charge
Enter the Values
Enter the Tax Paid by your pension scheme Box 11.2
Click SAVE