Four years. The special additional deduction for continuing education can be deducted for four years. According to the Interim Measures for Special Additional Individual Income Tax, the expenses for continuing education with academic qualifications generated by taxpayers receiving continuing education in China shall be deducted according to the standard of 400 yuan every month, and the deduction period for continuing education with equivalent academic qualifications shall not exceed 48 months, that is, 4 years. In addition, the expenses for continuing education of professional qualifications of skilled personnel and professional and technical personnel are deducted in the year when relevant certificates are obtained, and the deduction amount is 3,600 yuan.