I have been renting out a property for about 8 years through a letting agency.  I assumed that the letting agency was dealing with the tax aspects and so never sent in an income tax return. I recently became aware that I should send in a tax return and would like to know how far back the HMRC will want to assess my income.

The first thing is to make a calculation for each of the last 8 tax years separately to see whether a) you have actually made a net profit from your rental business (i.e. that your rental income is more than your allowable expenses), and b) that those profits are subject to tax (e.g. they are not covered by personal allowances or brought forward rental losses). If after these calculations you find that you owe tax to HMRC then your best option is to contact HMRC (before they contact you!) on the voluntary disclosure helpline on 0845 601 5041.