What the UK still taxes after you leave
Once you are non-resident under the Statutory Residence Test, the UK stops taxing most of your foreign income and gains but keeps taxing UK-source items. Rental income from a UK property stays within UK income tax under the Non-Resident Landlord Scheme, although you can apply on form NRL1 to receive rent gross and report it through Self Assessment. Gains on UK residential property remain UK-taxable for non-residents and must be reported and paid within 60 days of completion; the UK-France treaty does not take those gains out of UK tax. Pay for days you work in the UK often stays UK-taxable too. Ordinary UK private, occupational and state pensions generally become taxable only in France under Article 18 of the treaty, while UK government-service pensions normally remain taxable only in the UK under Article 19(2).
Timing decides how much you pay
You do not become non-resident just by leaving. If you qualify for split-year treatment, the departure year divides into a UK part and an overseas part, so foreign income after the split date generally falls outside UK tax; you claim it on the SA109 residence pages of your Self Assessment return. Watch the five-year temporary non-residence rule as well: if you were solely UK-resident in four or more of the seven tax years before leaving and return within five years, certain gains and income realised while abroad are taxed in the year you come back.
What France taxes
France taxes its residents on worldwide income, and its IFI wealth tax applies to worldwide real estate for residents (it is a real-estate tax, not a tax on all assets). The French impatriate regime is employment-linked, so it does not help retirees or self-initiated movers, and French rules are budget-sensitive, so confirm them with a local adviser. Our moving to France guide covers the departure steps, the treaty positions and the French points to check before you go.