Double Taxation Short Term Residency - Germany & UK

A person who studies in Germany normally and spends more than 183 days in the year in Germany. However, the person is doing an internship at a company in the UK and is over the tax allowance. The person will have spent 92 days in the UK and, according to the "Check your UK residence status" quiz, is a resident of the UK. The student has already paid tax to the UK since it was deducted from the source. There exists a double taxation treaty between the UK and Germany, but it is still not clear whether the person should be paying tax for the UK or for Germany? Kindly clarify. Thank you!

Hi Cedrik,
The individual will be required to complete a Self Assessment tax return and declare all of the UK earnings and tax deducted in supplementary pages SA102 to record employment income on your SA100 Tax Return. 
Self Assessment: Employment (SA102)
Use supplementary pages SA101 to record less common types of income, deductions and tax reliefs on your SA100 Tax Return. 
On SA101, box 12, declare that element of income which is not taxable in the UK.
Self Assessment: additional information (SA101)
A Self Assessment tax return can be completed online, tailoring the tax return to meet your needs. 
Please see guidance here: 
File your Self Assessment tax return online
Also for  more information, please contact our Self Assesment helpline:
Self Assessment: general enquiries
Thank you.