Linking your HMRC account, and what you are agreeing to
Every piece of MTD software asks you to grant it authority at HMRC, and almost none of them explain what that grant covers. It is worth understanding, because it is an authorisation against your live tax account and you should know its edges before you click through it.
The sign-in happens at HMRC, not here
You are sent to HMRC's own domain to sign in with your Government Gateway user ID and password. Taxmo does not see either, and cannot: they are entered on HMRC's page. What comes back is a token, and the token is what Taxmo holds. This is the same pattern behind any Open Banking connection, and it exists so that granting access never means handing over a password.
The authority is scoped
The grant is limited to reading and writing VAT. It does not extend across your HMRC account, and it cannot be used to see or change things outside that scope.
- Read your open VAT obligations, so returns are filed against the period HMRC has opened
- Submit a VAT return you have declared final
- Read a return you have already submitted, your VAT liabilities and your VAT payments
- Nothing outside VAT: not Self Assessment, not PAYE, not Corporation Tax
It expires, and it refreshes
HMRC issues a short-lived access token alongside a longer-lived refresh token, and software renews the first using the second rather than asking you to sign in again every session. If the refresh eventually fails, the honest outcome is that you are asked to reconnect. That is what a working implementation looks like: the alternative is a connection that quietly stops filing and tells you nothing.
Fraud prevention headers are mandatory
HMRC requires software to send a defined set of headers with each MTD call, identifying how the submission reached HMRC and from what device. HMRC publishes the specification, monitors conformance, and will chase vendors whose headers are wrong. This is why MTD software collects a little more context than a plain form would, and it is worth knowing so that the request looks like diligence rather than snooping.
Revoking it
You can withdraw the authority from your own HMRC account, without asking us and without needing us to be involved. That matters: an authorisation you can only cancel by emailing the vendor is not really under your control. Withdrawing it stops further filing and does not touch the records or the receipts already in Taxmo.
Common questions
What is a Government Gateway account and do I already have one?
It is the sign-in HMRC uses across its online services. If you have ever filed a Self Assessment return online or registered for VAT online, you have one. For MTD VAT it needs to be the account your VAT registration is enrolled on, which for most sole traders is simply their own.
Why does software need authority at all, rather than just a VAT number?
Because it is filing on your behalf against your live tax record. A VAT number is public-facing information and proves nothing about who is submitting. The authorisation is what tells HMRC that the return arriving from this software is one you sanctioned.
Can Taxmo see my Self Assessment or PAYE with this?
No. The grant is scoped to VAT read and write. A token issued for VAT cannot be used to reach other parts of your HMRC account, and this is enforced at HMRC's end rather than being a promise about our own restraint.
What happens if I change my Government Gateway password?
The existing authorisation generally continues, because it is a separate grant rather than a stored password. If it does stop working, you reconnect through the same one-pass sign-in. Nothing you have already filed is affected either way.
Do I have to reconnect for every return?
No. The authorisation persists and is renewed in the background. You would only sign in again if you revoked it or if the renewal chain broke, in which case Taxmo asks you to reconnect rather than failing silently.
Last updated 2026-08-10. Thresholds, rates and allowances are indexed or reset at fiscal events and are deliberately not quoted here; check GOV.UK for current amounts.