Thanks for your response I appreciate its all very confusing and that you do not understand how the tax code works, You are awarded an amount each year that you are permitted to receive in income each year tax free.
Usually we only have one source of income during our working life, and that's pay from employment - so the tax free allowances are turned into a tax code, sent to the employer (and you the employee) and the employer uses that code, to allow you some of your money each week or month tax free (as the free allowances are split into allowing you 1/52 of them each week or 1/12th each month, and anything over that amount liable to tax.
When you retire (or take on a second employment) then this becomes a little more complicated. In your case you then have pensions to think about as well as any employment you chose to take up/continue.
You still have one set of tax free allowances, but can have many sources of income I am sure you have at least state pension - and whilst tax is never deducted form it directly - its an income that is taxable, SO HMRC always take the state pension and reduce to tax free allowances you are due, so this income is fully covered for tax purposes.
Then, if there are any allowances left over - then these can be considered against any other source of income. In your case, it would seem there were no allowances left over after state pension was considered, so you either have a state pension of more than £10,000 OR have a state pension and another former employer pension, so all your allowances are utilised.
Meaning that the employment should have had full tax (so 20p in every £1 earned liable to tax) You advise that code BR has been issued - so this ensures that 20p in every £1 is taken from the employment - but I suspect there was a time that you were having NO TAX taken from this employment during 2012/2013 (so from 06/04/2012 maybe right through to 05/04/2013)
Now the question I need to establish is this
1) When did this employment start
2) Did the employer ask you to complete a form P46 (as you would not have had a P45 from a former employer, as you are a pensioner)
If the employer did give you a P46 (it asks you to sign a certificate stating what other incomes you may or may not have) did you give it back to them, If you are not sure about this P46 position, then might I suggest you ask your employer (without alerting them to the fact you owe the tax office money or they may not be honest with their answer)
If they state NO we did not give you a P46, then you can write to HMRC appealing this tax - I can help you draft a letter if you wish - as it can be argued it IS the employers fault
If they DID give you a P46, then you need to ask what certificate on the P46 did you sign, and it might actually be netter to ask them to provide you with a copy - then come back to me - let me know which certificate you signed, and I can advise from there.
If there is any way to appeal this unpaid tax, then I promise you I will find it for you