The UK tax doesn't get declared. It is irrelevant as far as the French are concerned. You are given a credit against the tax on your total global income, at the rate you would have paid tax in France. The level at which you pay tax is the level that corresponds to your global income. For example if you had a UK State pension it would be taxed in France but, if that was all you declared, you would only pay tax at the level that corresponds to it. That would normally mean, with the amount of UK State pension, that you wouldn't pay any tax on it but that would be inequitable as your total income, in the example you gave, would demand a higher level of taxation. Think of the various tax bands that apply. As an aside, if you are in receipt of a UK State pension, be clear when you are dealing with the French tax authorities, that it is equivalent to a French pension from one of the Caisses as the mention of the word "State" immediately makes them think that you were a fonctionnaire and that it is effectively a private pernsion. Just for the sake of clarity. Some years ago I was subject to a dip check by my local tax office. I went to see them and, as a result of that, I did a paper for them explaining the set up in UK regarding State pensions and private pensions.