HMRC is the most automated arm of the system you will deal with, and the hardest to step away from once you are inside it. If you are employed under PAYE, your employer deducts tax at source under a statutory scheme that the legal person is presumed to have joined the moment a National Insurance number was issued in that name.
The lawful position is the same as anywhere else: a living man or woman cannot be taxed without consent. Statute applies to legal persons. The trick of the income tax system is that it presents itself as universal and treats the registration of the legal person as evidence of consent by the living being.
What you can and cannot do
Realistic position first. If you are a PAYE employee, your employer will continue to deduct tax and send it to HMRC regardless of what you write to anyone. The employer is acting on their own statutory obligation, not on a personal duty owed to you. You cannot make them stop by writing to HMRC, and writing to your employer in lawful terms will, in most cases, end the employment rather than the deductions.
What you can do is start the long move. Reduce dependence on PAYE income. Move toward self-employment, contract work paid gross, or trading in your own name as a living man or woman with a separate book of account. From that position, the lawful question of consent becomes live, because there is no employer standing between you and the demand.
For self-employed work, the sequence is the standard one. Demand from HMRC. Notice of Understanding and Intent. Conditional acceptance asking for the contract under which the living being consented to be bound by the Income Tax Act and the proof that the income in question is taxable on the man rather than on the legal person. Notice of Default if ignored.
Hold the line
HMRC will not engage with the lawful argument in writing. Their letters will continue. They may issue assessments, penalties, and eventually pass the matter to debt collection or apply to court. The lawful position does not, on its own, stop their machine. What it does is build your record so that when you eventually move to a different income structure, you have a paper trail showing you never accepted the basis of their claim against you.
This is a long game. Anyone who tells you that one letter to HMRC will end your tax obligations is selling something, and what they are selling will get you fined. Move slowly, keep your records clean, and treat each year as a step.