Work for foreign company while living in the UK

I am moving to the UK in a month while still being employed with my German employer. My employer does not have a UK office or presence of any sort, so I will be working fully remotely. The original plan was to be exempt from almost everything at source in Germany apart from the insurances that are equivalent to the UK National Insurance. The difference to UK taxation would then be paid by filling out my own UK tax return. Upon calling the German insurances, they confirmed I could keep paying into them even without residency in Germany, and on the HMRC hotline it was confirmed that I can choose to pay into my state pension and other state insurances either at source or in the UK. However, while preparing those steps of getting me exempt, or ,respectively, staying in the German insurances, my workplace's payroll department has raised the issue that this scenario may not be possible after all, and while they are still confirming this with the insurances in question, that has raised the following question for us: In case I cannot pay the German insurances which are equivalent to NI at source in Germany whilst working in the UK, I would be able to pay the employee's contribution to the NI with filling my UK tax return. But what happens to the employer's contribution in this case, which would normally be paid in Germany? 1) Does the employee (i.e. me) also need to cover the employer's NI contribution when filing the tax return, or 2) is the employer still going to pay his contribution into the German system, or 3) does the employer somehow need to pay his contribution into the UK system (if so, how would this work?), or 4) is the employer's contribution not going to be paid at all, or 5) is this issue solved a completely different way? I would be very grateful if you could help with this concern and lay out what course of action the different tax systems and treaties between Germany and the UK provide for regulating cases like this.

Hi
As your employer is within the EU and has no UK premises, you will need to establish if you meet any of the following: Withdrawal Agreements, Trade and Co-Operation Agreement or UK-Ireland 2019 Agreement. If none apply, then you, as the employee, can register for either a DPNI scheme (tax and employee national insurance only) or a DCNI scheme (employee national insurance only) and report your tax via Self-Assessment. If you fall within one of the agreements, then your employer is required to register for PAYE purposes. Your employer can either register for an NI only scheme (both employer and employee national insurance) and you would declare your tax via Self-Assessment or they register for a full PAYE scheme to report and pay any tax and NI contributions to HMRC. To register a PAYE scheme, you or your employer can contact the Employer Helpline on 0300 200 3200. If you need assistance in determining whether you fall within the agreements mentioned above, you can contact the International Caseworkers on 0300 200 3500. Unfortunately, we are unable to comment on whether your employer is required to pay anything in Germany. They would need to contact the appropriate German authorities.