When UK tax stops
Your position turns on the Statutory Residence Test, a day-counting and connection-factor test. While you remain UK resident you are taxed on worldwide income; once non-resident, the UK generally taxes only income arising in the UK and gains on UK land. If you keep a UK home, family or significant work here, you can stay UK resident even while living in Germany. Most leavers who meet a statutory case, such as starting full-time work overseas or ceasing to have a UK home, qualify for split-year treatment, dividing the departure year into a resident part and a non-resident part. Report leaving on the SA109 residence pages of your Self Assessment return; file a P85 only if you are not in Self Assessment.
What the UK still taxes after you leave
UK rental income stays fully UK-taxable under the Non-Resident Landlord Scheme; registering with form NRL1 lets you receive rent gross and settle the tax through Self Assessment. Gains on UK residential property remain chargeable and must be reported and paid within 60 days of completion, even where there is no tax to pay. Most UK pensions remain taxable somewhere, and the UK-Germany treaty decides whether the UK or Germany taxes each type; in many cases Germany, not the UK, taxes private and occupational pensions. If you return to the UK within five years, the temporary non-residence rule can also tax certain gains and income realised while you were away.
What Germany will tax
Germany taxes its residents on worldwide income, including your UK-source items, with treaty relief preventing full double taxation. There is no flat-rate expat regime, and a solidarity surcharge and, for church members, church tax can apply on top of income tax, so take local German advice. Our Moving to Germany from the UK guide covers the full departure checklist, pensions, property and the five-year rule in detail.