Compulsory Attendance Age
Pre-school is mandatory from age 5, and the state and local authorities must secure the necessary conditions for encompassing all children in that age (Art. 8, Sec. 1) School is mandatory between ages 7 and 16, where the starting year can be age 6. (8(3). Kindergarten begins at no earlier than 3 years of age, not mandatory.
Estimated Number of Homeschoolers
Estimated number is several hundred families, approx. 400-500. Seek other sources as well.
Private schools must follow government educational standards and must be licensed by the state (Ministry of Education). Art. 38-40.
Homeschooling is not expressly forbidden but the law does not provide for home education independent from the government education programs and standards. One can choose an "independent form of education" if the parent or the student chooses so. This format is also subject to testing and oversight by the state school system and the student must be affiliated/enrolled with a school and follow their curriculum. (Art. 112, Sec. 2)
The state education authorities evaluate and issue a decision when parents choose the independent format. If the student does not meet their standards, the appointed educational commission can mandate switching to regular school attendance. The students follows government curriculum. Regional education authorities exercise control over the independent student's education progress (Art. 112, Sec. 4-7; Art. 210, Sec. 2).
The government took action in 2017 to mobilize groups of social workers, medical and education workers and police to visit the homes of parents with children who do not attend state school, or other schools listed in the law.
There are fines of 50 to 150 BGN ($30-90) for parents who do not enroll their children, or do not make sure their enrolled children attend school (Art. 347). Repeat offences are subject to fines of up to 500 BGN ($300).
If social services decided that a child is neglected and at risk due to not attending school, they may pursue revocation of parental rights. There are no such cases known to me, in the last few years in Bulgaria, against homeschoolers.