What You Need to Do
If Your Dividend Income Is £10,000 or Less
If you do not currently file a Self Assessment return and your dividend income for the year is £10,000 or under, you do not need to register for Self Assessment just for this. Instead, you need to tell HMRC directly, either by having the tax collected through an adjustment to your tax code, or by calling HMRC on 0300 200 3300 (lines are open Monday to Friday, 8am to 6pm).
In practice, an adjustment to your tax code is usually the less painful route if you are employed or receive a pension, since it spreads the amount owed across your future pay rather than asking for a lump sum.
The phone route can work well too, but as the original taxpayer in this story discovered, it is worth having your dividend figures ready before you call, along with a clear idea of which category you fall into, so you are not passed between forms that do not seem to match your situation. It is worth checking the detail on declaring dividend income before you pick up the phone. This is also the kind of thing why people choose Pie Tax in the first place, since it flags what you owe well before any deadline creeps up, rather than leaving you to piece it together from a bank statement in September.
If Your Dividend Income Is More Than £10,000
If your dividend income for the year comes to more than £10,000, the informal route is not available to you. HMRC requires you to register for Self Assessment and file a full tax return, even if you have never needed to do one before. You need to tell HMRC that you need to register by 5 October after the end of the tax year in which you received the income (the tax year itself runs to 5 April), and from there you will complete a return covering not just your dividends but your full financial picture for the year.
This is a bigger commitment than it sounds, since registering for Self Assessment means setting up a Unique Taxpayer Reference and getting familiar with a system that has its own separate deadlines for online filing and payment. Our guide on registering for Self Assessment and meeting the deadlines covers what HMRC will ask for and how long the process typically takes. Once you are registered, our piece on reporting dividend income on Self Assessment walks through exactly which boxes to use and what records to keep, from dividend vouchers to platform statements, and how Pie Tax works shows how much of that can be handled for you automatically rather than pieced together at the last minute.