All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
In principle there is no harm, Insha Allaah, in working as an accountant since it is among the beneficial jobs which leads to many benefits. So accountancy is permissible as long as it does not contain a prohibition. If it contains a prohibition, like calculating interests, then it is not permissible to work as such. Allaah says (interpretation of meaning): {...but do not help one another in sin and transgression...}[5: 2].
As regards the company you want to work for which provides wrong information about its real profit to avoid paying taxes, you have to know that imposing taxes on citizens without any right is one of the major sins, be it from a Muslim or a non-Muslim country. This is taking people's money without any right, and Allaah Has severely warned us against this. Imaam Ahmad reported that 'Uqbah Ibn 'Aamir narrated that the Prophet said: "The one who forcefully takes taxes from people will not enter
With regard to this company disregarding the laws applied in accountancy, if these laws are not contrary to Islamic legislation, and it is the government that legislated them for the public benefit, then it is not permissible for you to work for this company. Because when a Muslim enters a country with a pact, he has to abide by it if it does not contradict the Islamic legislations. Allaah says (interpretation of the meaning): {And fulfill every covenant. Verily, the covenant will be questioned about.}[17:34].
But if these laws or other professional practices are contrary to Islamic legislations, then there is no harm for you to work in this company even if your work requires you to overlook these laws and practices as they have nothing to do with Islam.
Allaah knows best.