Self assessment statement vs tax calculation

The figures between my statement and tax calc do not correspond. Does anyone else find they are difficult to interpret? I am thinking that I would need to physically show both documents to a tax adviser

To be more specific the balancing payment as shown on the Tax Calculation is not the same as the balancing payment (minus pre existing balance) as show on the Self Aessment statement.

I think that is normal. In my experience, the balancing payment on the tax calculation at the end of filling in the return, takes into account the figures reported in the return itself only. I have needed to adjust it myself to take account of a pre-existing balance, when deciding how much to actually pay.