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![What is a Self Assessment tax form SA100?](https://cdn.prod.website-files.com/5d71eeb2a19ee03e3430f50f/6235cf5ce85f6f4d9622d7aa_what-is-a-self-assessment-tax-form-sa100.png)
The SA100 is the main document you need to fill when completing your Self Assessment tax return. There are two ways to complete your Self Assessment tax return: you can make an online submission, or download the form SA100 and make a paper submission.
The SA100 is the main document you need to fill when completing your Self Assessment tax return. There are two ways to complete your Self Assessment tax return: you can make an online submission, or download the form SA100 and make a paper submission.