There aren't any specific academic qualifications that employers ask. However, you will benefit from good levels of general education, possibly with maths. Some employers want you to have GCSEs including maths. Your ability to number-crunching, computer skills, etc are also important. You will benefit from good communication skills, ability to cope with pressure and a good understanding of the legislations regarding debt recollection.

Once you are in the job, you will usually be required to undergo training, which includes teaching of everything you need – telephone skills, management capabilities, credit/recollection laws, debt recollection procedures, etc. You can also take qualifications from such institutes like Credit Services Association or Institute of Credit Management. Diplomas by CSA, City & Guilds, ICM, etc are beneficial, which you can take up after starting working as a credit controller.