An Individual Savings Account (ISA) is a tax-advantaged account available to UK end users. Upvest offers an end-to-end API solution for moving funds into an Upvest-supported Stocks and Shares ISA. A transfer moves cash from an end user's existing ISA into their Stocks and Shares ISA without consuming the current year allowance twice: the portion that relates to the current tax year is carried across and applied to the receiving wrapper's allowance.
The Investment API currently supports transfers within the same ISA manager. These are the transfers an end user makes when they move money from a Cash ISA to a Stocks and Shares ISA held with the same client. Because both wrappers sit with the same ISA manager, there is no counterparty to negotiate with and no market instruction to send, so the transfer settles directly.
Transfers between different ISA managers, outgoing transfers, and in-specie settlement are not yet available through the Investment API. The API has been designed to accommodate them, and they are planned for a future release.
| Key term | Description |
|---|---|
| ISA manager | The firm responsible for administering an end user's ISA and reporting it to HM Revenue & Customs (HMRC). A client is the ISA manager for the ISAs it offers. |
| Transfer within the same ISA manager | Moving funds between two ISAs held with the same ISA manager. Typically a move of cash from a Cash ISA to a Stocks and Shares ISA. |
| Incoming direction | The direction of funds is from another ISA into the Upvest-supported Stocks and Shares ISA. |
| Cash settled transfer | The transfer is made as cash. Where the source ISA holds instruments, they are sold first and the resulting proceeds are transferred. |
| Current year subscription | The part of a transfer that relates to money the end user paid into an ISA during the current tax year. It counts towards their annual ISA allowance. |
| Previous years' balance | The part of a transfer that relates to earlier tax years. It does not count towards the current year allowance. |
A transfer within the same ISA manager moves cash from an end user's existing ISA into their Upvest-supported Stocks and Shares ISA. The client is the ISA manager on both sides, so Upvest has no visibility of the source ISA. You supply the cash amount and the current year subscription details with the transfer request, and Upvest uses them to credit the account group and apportion the transfer against the annual allowance.
Previous years' balances move across without affecting the end user's current year allowance. Where part of the transfer relates to the current tax year, that portion updates the allowance on the receiving Stocks and Shares ISA, and you update the allowance on the source ISA to reflect the change.
Initiation
The end user requests the transfer in your application. You create the transfer through the Investment API, supplying the cash amount and, where applicable, the current year subscription details. The transfer is created with status NEW.
Processing
Upvest processes the transfer and moves it to status PROCESSING. Because the transfer stays within the same ISA manager, there is no discovery or market instruction stage.
Settlement
The cash is credited to the end user's account group, the current year subscription is applied to the ISA allowance, and the transfer reaches status SETTLED.
You track each stage through ISA transfer webhooks rather than by polling.
The ISA allowance is tracked against the tax wrapper, not the transfer. When a transfer that includes a current year subscription settles, the subscription amount is added to the used amount of the receiving wrapper's annual allowance and an ISA_WRAPPER_ALLOWANCE.UPDATED event is sent.
For how allowances are created, read, and renewed, see How to integrate ISA tax wrappers.
The rules related to ISA transfers are set by the Financial Conduct Authority and HM Revenue & Customs, and are subject to change. The 2025 Autumn Budget ISA reforms set out future changes that restrict transfers into Cash ISAs, taking effect from 6 April 2027. Refer to the FCA and HMRC websites for the most up-to-date information.
According to the UK government, the ISA transfer process should take no longer than:
- 15 working days for transfers between Cash ISAs
- 30 calendar days for other types of transfer
- How to implement ISA transfers — scopes, request and response fields, and the transfer lifecycle.
- ISA transfers webhooks — the events Upvest sends as a transfer progresses.