Hi again.Rental income is taxable. Take a look here for more information on that. I'm afraid that you have left yourself open to the possibility of tax based penalties for your failure to disclose and for late payment of any tax which might be due. You can read about those here and here.You need to complete a tax return if your rental income exceeds £10,000 per annum before expenses (your share) or £2,500 after expenses (your share) as you will read here. You can in certain circumstances choose to have any tax payable collected through your tax coding if you have a PAYE source of income which you both do but this may not be possible for the years that you have missed disclosing the income for. Therefore, you both may need to register for self-assessment which you can each do using Form SA1. You can also register online here.If I were you, I'd complete an income and expenditure account for each tax year that you have let the property and divide the income between you and your partner. A property owned by a married couple or those in a civil partnership will be deemed to be owned on a 50:50 basis unless it is actually owned in proportions other than 50:50 and a completed form 17 is lodged with HMRC. In the absence of such a declaration, the income will be split 50:50 for tax purposes which may or may not be to your advantage depending on the level of your respective incomes.Before you register for self-assessment, I would suggest that you send your rental income statements to HMRC with a letter explaining the situation and making your apologies. As many people have been in the same situation as you and your partner as regards ***** ***** HMRC have a procedure they follow which doesn't always require the completion of tax returns for earlier years. They simply assess the tax due, along with any interest and penalties. Penalty charges can be appealed against as you will read here. HMRC may ask questions before they get to the point of calculating any tax liabilities. If you run into a particularly officious or difficult HMRC officer, you might consider asking an accountant or a tax adviser to handle the matter for you, for a fee of course.I hope this helps but let me know if you have any further questions.