First of all, let us try to understand both of them separately and then we will move to relationship between them.Minimum alternate tax or MAT is applicable for Companies and Limited Liability Partnerships (LLPs) wherein the company or LLP is required to pay a minimum tax based on the book profit of the company. Without the concept of MAT, a large number of companies and LLPs were having book profit as per their profit and loss accounts but were not paying any tax since their income computed as per the Income tax act was either, NIL or negative or insignificant. Thus, to regularize such tax payers, the concept of MAT was introduced in India.Corporate tax is regular income tax calculated on income of companies calculated as per Income Tax Act 1961.Any company that pays minimum alternate tax under the MAT clause instead of regular tax, then if the tax paid is more than that accrued, the excess amount is credited back as tax credit to the company. Thus, MAT credit can be understood as the difference between the tax calculated under the general provisions of the Income Tax Act and that calculated under the MAT provisions of the Act. Such excess of tax credit is allowed to be carried forward and set off in the financial year in which the company is liable to pay tax under the general provisions of the Income Tax Act. This MAT credit can be carried forward and set-off for 10 consecutive assessment years succeeding the year in which the tax credit first accrued.I hope, I was helpful.Please feel free to comment.