Thanks for requesting me.
Naturalisation relies on his time in the UK and he is no longer dependent on the relationship or on you exercising your treaty rights in the UK, so he primarily needs to evidence his time in the UK and his employment and finances.
It is also part of the application to evidence the residential period as well - many people think it is only the additional year after ILR that needs to be evidenced. As the residential period relied on his relationship with you it is therefore a good idea for you to also include your passport and some payslips/previous P60 documents. It certainly cannot hurt the application and it enables a 'difficult' caseworker to see that ILR was correctly granted and thus that the residential period was in accordance with the terms of the visa.
So, to summarise, evidence his time in the UK and his employment and finances (if self-employed it is important to show he is registered as self-employed and paying National Insurance contributions - HMRC can provide confirmation), show that you are still living together and that you are still exercising your treaty rights and also show that he has passed the Life in the UK test. If applying from October then English language must also be evidenced.
This will be more than sufficient to enable any caseworker to approve the application, assuming no other issues in terms of criminal convictions, etc.
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