Last updated on:
March 17, 2024

The SA100 form serves as the backbone of the Self Assessment tax return for those who opt for the traditional route of paper filing. It's essentially your way of communicating your annual financial affairs to HMRC, covering everything from income and deductions to reliefs and taxes owed. This comprehensive document ensures you account for various income streams, from employment to investments, and allows you to claim any deductions or reliefs you're entitled to.

Filing the SA100 by post involves a bit of preparation, as you'll need to ensure that all relevant supplementary pages are attached, depending on your sources of income or the claims you're making. For example, self-employment income or rental income each has its own specific supplementary form that needs to be filled out alongside the SA100.

HMRC has made the SA100 form accessible on their website, simplifying the process for those who need to download, print, and manually fill out the form. Remember, the deadline for paper submissions is notably earlier, on October 31st, than the online submission deadline, which extends to January 31st of the following year.

For those who have previously filed a tax return, HMRC may pre-emptively send you an SA100 form by mail, streamlining the process for you to complete and return. Yet, for many, the convenience and extended deadline of online filing are compelling reasons to transition from paper to digital submissions, negating the need for handling physical documents like the SA100 form.

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