Hi,
If you have foreign employment income, this should be declared in box 1 of the employment section of SA102. For foreign self employment income, it is declared on SA103:
(
Self Assessment tax return forms). This adds the income into the tax calculation. The foreign page SA106 would only be needed if you had to pay tax in an overseas country on the income, because of the tax treaty. You would then be able to claim a foreign tax credit (
Tax treaties).
Thank you.