Can I register for Self Assessment by post instead of online?

Yes. If you're self-employed, you can download and post form CWF1. If you have other untaxed income (rental, dividends, capital gains), use form SA1 instead. Both are available on GOV.UK. That said, the online route through the HMRC website is faster and means you'll get your UTR more quickly. If you're not sure which form applies to you, message us on live chat.