It is unlikely you can add more to a fixed term account. Furthermore you cannot normally open more than one cash ISA in any one tax year. That said you should contact the Halifax to check. You can normally invest up to £5,340 in cash ISA this tax year and £5,340 in stocks & shares ISA. The ISA limit increases to £11,280 in the new tax year, commencing 6th April 2012 of which £5,640 can be in cash ISA.

Disclaimer:
The answers above are for guidance only and should not be acted upon without you receiving independent financial advice relevant to your circumstances. Please note tax rules are subject to change. To find an IFA please go to http://www.unbiased.co.uk

Danny Cox, Certified Financial Planner CM, Hargreaves Lansdown, www.hl.co.uk/news/danny-cox Twitter @DannyCoxIFA