Why declare net interest?

Under the heading "UK interest (bank and building society, PEP and ISA, National Savings and Premium Bond winnings", the article states: “Declared in total, jointly, for both spouses. Add together all of the net interest and winnings for both spouses, from all sources, by country of origin.”
Please could you confirm that net interest is correct and I thought everything was declared gross. If net is correct could you please explain why this is.

Both of your questions are being answered together as in a way they are part of the same reply, although there is a difference in what needs to be “declared”, on the one and, and what is “assessed” to tax on the other.

So, as UK bank interest is paid after the deduction of UK income tax, it is received net.

The other income sources are generally exempt from income tax, so are also paid net, although this figure will, admittedly, be the same as the gross income.

The French require that it is the net income received that is initialled “declared” on the form 2047, as there is then a method of accounting for the income tax in order to then produce the gross income which, yes, will be “assessed”.

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