Business income

Self-employment profits and limited company dividends need to be declared every year.

Rental income

If you're a landlord, own a holiday let, or have any other income from land and property, the chances are you need to do tax returns.

Capital Gains Tax

CGT on profits on the sale of e.g. property or shares needs to go on a normal tax return. Plus if you sell a residential property that is not your own home you may need to declare and pay the CGT within 60 days of sale.

Investments

You may have interest, dividends etc from investments (e.g. a managed portfolio) to declare each year.

Construction Industry Scheme

CIS subcontractors are their own self-employed business and even though tax is deducted during the year, they still need to do accounts and a tax return each year.

Employment income

You might be happily employed by someone else, but still need to declare benefits and claim expenses to do with your job.