Here's a date for your diary - 31 January 2020. That's the deadline to submit your tax return online for tax year April 2018 to April 2019 via the Government Gateway portal.
Details are at www.gov.uk/self-assessment-tax-returns. You face an automatic three-figure fine if you don't submit a tax return by that date. Don't say we didn't warn you.
If you haven't sorted out a Government Gateway account and got a password (by post - it can take a while to arrive) do so now. The deadline for tax returns on paper is 31 October 2019.