Your Tembo ISA is only classed as "open" once you fund the account - either by adding money to the account via a one-off contribution or direct debit payment or by transferring funds from another ISA.

However, you can "set up" an ISA account in the Tembo app, then pay in or transfer in funds into the account at a later date to officially "open" the account.

So if you've already met your ISA allowances for this tax year, you can set up a Tembo account before the tax year ends as long as you don't pay or transfer any funds in until the new start year starts. As soon as the new tax year begins and your ISA allowances reset, you can fund your Tembo account.