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HMRC internal manual

Self Assessment Manual

Returns: filing returns online: introduction

An individual or agent can file online the SA100 individual’s tax return, trust return and partnership return. They can register for the service by visiting and selecting `Log in and file your Self Assessment Tax Return’. Full information on filing online is available on the web site.

Once the customer has successfully registered for the SA Online Service they will receive an Activation Code. This Code is sent through the post by the Government Gateway within 7 days of enrolment and should arrive within 10 days (21 days if it is being sent abroad). The customer should then log into SA Online and activate the service. The service must be activated within 28 days of the date shown on the Activation Code letter.

A taxpayer can then

  • File their form SA100, trust return or partnership return. Note: HMRC software covers the SA100 main tax return plus supplementary pages in respect of employment, self employment, individual partnership, UK property and foreign income. Third party products are available to  offer other supplementary pages that HMRC does not cater for
  • File attachments electronically with the return. Note: Some third party products will also offer electronic attachments
  • View the status of tax returns for all SA years (date issued, date due, date received) and details of any returns outstanding
  • Submit a claim for repayment
  • Submit a claim to reduce payments on account
  • View their statements online
  • Ask a question about the SA process and have the opportunity to search through a series of frequently asked questions. If unable to find the answer they can send an email and receive a reply direct into their own secure mail box
  • Change their name, address and contact details
  • Add, change or delete agents
  • Choose to receive notifications and reminders by email or text message
  • Make payments electronically

Agents who have successfully activated their service can

  • File form SA100, trust and partnership returns on behalf of their clients
  • File attachments electronically with the return on behalf of their clients
  • Submit a claim for repayment
  • Submit a claim to reduce payments on account
  • Change name, address and contact details
  • View information on their clients’ Self Assessment statements of account
  • See and download their clients in a list (up to a maximum of 4000 clients) on screen

Further information is available in subject ‘Structured Action Requests’ (SAM126090).

Note: Whenever there is a change to the capacity details, any current registration or enrolment for the SA Online Service will be removed from the online computer system. Therefore the capacitor must be advised to register and enrol again for the SA Online Service, using the personal details of the customer they are acting for, to be able to file the customer’s tax return online. When this is done, the activation code will be sent from the Government Gateway to the home address of the capacitor on the record. For further information see subject ‘Set up taxpayer record: set up capacities’ (SAM100210).

SA Online is available for original returns (including re-submission of rejected returns) and amended returns.

The SA Online service supports the submission of previous years returns from 2011-12, and normal penalties still apply in respect to late tax returns. Further information regarding ‘Penalties’ can be found at SAM61000 onwards.

SA Online accommodates the receipt of exactly the same information as appears on the paper version of the returns. You are also able to view the full return filed online and any additional information details where required, including attachments filed electronically with the return.

Individuals and Partnerships

The information received online in respect of form SA100 and partnership returns will be subjected to the same computer checks for basic errors of transposition or arithmetic as the paper return. Only where all the information is acceptable will the customer’s SA record be updated.

(This content has been withheld because of exemptions in the Freedom of Information Act 2000)

(This content has been withheld because of exemptions in the Freedom of Information Act 2000)

Where the return information fails the computer checks, an online message (and an email where an email address is provided) will be sent to the customer and the return is deemed not to have been received.


Trust returns, original or amended, will not be logged or checked by the system when they are received, nor will information from them be passed to the SA computer system. It will therefore be necessary for trust returns received online to be logged on SA and captured using the SA Trust Return application, in the same way as a paper return.