Benefits/disadvantages of employer paying tuition fees

I completed first year of my studies and got a p/t job in firm relevant to my studies. I am going back into second year p/t and my employer is open to keeping me on the two days i'm off. I'm considering approaching him to pay my fees/ negotiate paying part. They are not too bad - €800.
Question is - can he write off this expense? How do i present this proposal to him as a benefit apart from me gaining new training/studies. Can he only claim 20% back as i found in other topic on the boards.
I know i won't be paying BIK as its relevant to my employment, but can my employer impose a pay cut as i'll be "training"? . I currently get paid €10 p/h

Thanks

Can't comment on the tax side of things but I'm sure others will do so in due course.

One of the disadvantages can be where employers have an education policy and get people to sign up to stay with the company, after they have completed their course, for the equivalent length of time that it took to complete the course. So if you complete your course in 3 years you will be tied to them for 3 years.

In the company I work for - you have to give them back 5 years. If you leave within the 5 years you have to refund the company the money.

Also - the company I work for - works it - that you dont get the money unless the exams are passed. Repeat exams are not paid for.

The company reclaim the tax. it is not worth that much anymore as the government has reduced the amount to claim back.