Retired and moving to UK

My husband is moving to UK when he gets his visa. We are retired and would like to know about my husband completing a US return and UK return. Is his Social Security taxable here if it is paid into a US bank account? What about interest from US banks is that taxable here? What does he have to show on his US tax return? We aren't going to work, we shall live off savings and His Social security. HELP it is very confusing to us.

Can you post please .... what are the nationalities of you and your husband?

I'm British and husband is US citizen

Sadly - annoyingly to my mind - this is one of the most complicated sets of situations.  You will need to budget for a dual US/UK qualified tax adviser to assist with both planning and twice annual tax filings for you both.