Hi,
Article 15 of the UK/china tax treaty related to employment income and advises that employment income earned while in China is taxable in China, but if in the UK when earning the income, then it is taxable in the UK as foreign employment income, provided you spend less than 183 days in any 12 month period in China.
This would be declared on a self assessment tax return.
Income from RSUs would fall under the guidance below.
UK/CHINA DOUBLE TAXATION AGREEMENT SIGNED 27 JUNE 2011
If taxable in the UK, and combined by your employer into your income, you would declare on page SA102, with any tax deducted on SA106, so that you can claim a foreign tax credit.
If separate from your employment income, you would show the vested shares in the box marked "Tips and other payments not included on your P60".
Thank you.