The deadline to open a H2B ISA is November 30th - you must be 16yrs old to open one. A 16yr old with a stocks and shares CTF only has the option to secure it in a junior ISA. I believe they should have the option of placing it in a H2B ISA to give them a head start on buying their first home
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The first deposit into a H2B ISA is capped at £1200, then monthly deposits capped at £200 after that. A CTF should be able to be used for this first deposit and any surplus in the CTF placed in a standard junior ISA .