Next year

We had a 1 year fixed rate end the last of Feb. We just added more money and rolling it over for another year. I kind of assume that the amount of % increase we got will go on the 2019 taxes like it would if you had a savings account even if you don't take it....yes? Unlike a mutual fund that doesn't get zapped until you take it out.

HMRC will tax the interest as it arises. If you had access to the interest earned after year 1, even if there was a withdrawal penalty, you declare the interest to HMRC within the tax year the interest was paid. The same applies to 2, 3, and 5 year term accounts.

I have numerous 1 year fixed term accounts. Most are automatic. I don't have to do anything, even reply. If I don't reply, the account automatically rolls over and reinvests the basis plus the interest for another 1 year fixed term. I declare the interest earned at the end of each respective tax year to both HMRC and the IRS.

https://www.telegraph.co.uk/money/ask-a-money-expert/when-does-the-interest-on-my-fixed-rate-bond-contribute-to-my-pe/