Sub-processors
Last updated: 29th October 2026
About This List
Where an accountancy firm, bookkeeper or other business uses Tax Optimiser to hold personal data about its own clients, that business is the data controller and Tax Optimiser Ltd acts as its data processor (see clause 11 of our Terms of Service). A sub-processor is a third party we engage to process that personal data on our behalf so that we can provide the Service.
Each sub-processor below is bound by a written contract that requires it to protect the data, process it only to provide its service to us, and meet obligations equivalent to ours under the UK GDPR. How we handle personal data more generally is set out in our Privacy Policy.
Current Sub-processors
| Sub-processor | Purpose | Data processed | Location | Transfer safeguard |
|---|---|---|---|---|
| Microsoft Azure Microsoft Ireland Operations Ltd |
Hosting, databases, file storage, encryption key management, logging and application monitoring | All Customer Data held in the Service | United Kingdom (UK South) | Not applicable: primary data is held in the UK |
| Anthropic Anthropic, PBC |
AI features, such as reading uploaded trial balances and VAT workbooks and suggesting account categories | The content of documents and figures you send to an AI feature | United States | Approved UK transfer safeguard (see International Transfers). Data sent through the API is not used to train models. |
| Postmark ActiveCampaign, LLC |
Delivery of service and transactional emails | Recipient names and email addresses, and email content such as filing confirmations and reminders | United States | Approved UK transfer safeguard (see International Transfers) |
| Stripe Stripe Payments UK Ltd and affiliates |
Subscription billing and payment processing | Billing contact name, email address and payment details | United Kingdom, United States | Approved UK transfer safeguard (see International Transfers) |
Website Providers
These providers process data about visitors to our website only. They do not have access to Customer Data held in the Service.
- Google reCAPTCHA (Google Ireland Ltd): spam and abuse protection on sign-up and contact forms.
- Tawk.to (tawk.to inc.): website live chat, loaded only if you accept optional cookies.
Recipients You Choose
The following are not our sub-processors. They receive data only when you ask us to send it to them or choose to connect them, and they process it under their own terms:
- HM Revenue & Customs and Companies House, for returns and filings you ask us to submit.
- Accounting, banking and practice platforms you connect, such as Xero, Sage, QuickBooks, QuickFile, Starling Bank, Karbon and Sodium.
Changes To Our Sub-processors
Our customers give us general authorisation to engage the sub-processors listed on this page. Before we add or replace a sub-processor that will process Customer Data, we will update this page and email the account owners of affected customers at least 30 days in advance.
If you have reasonable data protection grounds to object to a new sub-processor, email privacy@taxoptimiser.co.uk within that 30-day period. We will work with you in good faith to resolve the objection. If we cannot, you may stop using the affected part of the Service or close your account.
Change History
| Date | Change |
|---|---|
| 29 October 2026 | List first published as a separate page. No change to the sub-processors we use. |
Contact Us
For questions about our sub-processors or to request a copy of our data processing terms, email privacy@taxoptimiser.co.uk.
