I am a US citizen living in the UK with my British husband. Do I have declare all the interest we received for the joint account we hold in a UK bank? Or only half of it?

You would declare your ownership percentage of interest income if the account belongs to both of you and you have signature over that account.

Married filing separately: You don’t have to report their foreign financial accounts if you don’t have signing authority over them. So if your spouse is not a US person and they own financial accounts, bank accounts, brokerage accounts overseas that you don’t have access to, that you don’t have signing authority over, then those accounts do not need to be reported.

• Summary of FACTA Reporting - Use this link to see if you are required to file Form 8938 with your tax return.

• Why can't I file my 8938 form? - Use this link for an update should you need this form.

So if we both my husband and I are "owners" of the account, does that mean that I am only responsible for half of the interest?

Yes.  If you are equal joint owners on the account then you should report half the interest on a married filing separate return. This means you have the authority to withdraw, signature over the account with the same control as your husband.

• Do I need to report foreign income?