The maximum you can pay into your Dodl investment ISA is £20,000 per tax year. This is your ISA allowance, set by the government and applies to all your ISAs collectively. So if you’d already paid £1,000 into a cash ISA you hold, you could only pay £19,000 into your Dodl investment ISA. It’s an annual allowance, which resets at the start of each tax year (on 6 April).