A letter of exemption is an official document, which is rather difficult to draw up without special legal knowledge. In addition, you need at least basic knowledge of business ethics and office work. The main task here is to clearly formulate the reasons for the refusal and the reasoning that you are going to give. As a rule, argumentation should be presented in ascending order: from less powerful to more advantageous.
Choose a writing strategy. The whole style will depend on it. It is better to avoid extremes here - too excuseful or too aggressive style, since both of these options usually turn out to be losing. The standard reaction to them is unwillingness to further communicate with the sender of the letter. The use of too long sentences and reduced, colloquial vocabulary is also stylistically unjustified.
At the beginning of the letter, it is better not to list the reasons for the refusal and not start with an apology. On the contrary, it can be a profitable strategy to indicate at the beginning of the letter the regulations on which you intend to formulate the waiver.
The reasoning in the letter needs to be thought out especially carefully. It constitutes the bulk of its informational part. Give only real arguments, and the same thing can be repeated several times in different words. It is not recommended to use evaluative vocabulary as it creates a sense of bias.
Please provide quotes or excerpts from official documents that you have adopted. This will make your disclaimer appear reasonable and discreet. As official documents, you can be guided by legislative acts or other legal documents, such as, for example, the Labor Code, GOSTs, technical regulations, etc., as well as the internal regulations of the company.
Provide evidence for all the facts you listed. If you need to write something impartial, you can resort to allegory, veiled expressions, hints.
Make a waiver letter on the form and certify it with the signature of the director of the enterprise and the relevant department.