In short: A universal pension fund (UPF) is Bulgaria's compulsory second-pillar fund, in which every insured person born after 31 December 1959 has a personal pension account.
Simply put: In some countries part of the compulsory pension contribution goes not to the state but to a personal fund. In Bulgaria this fund is called "universal". The money is recorded in your name and invested; at retirement it pays a supplementary pension on top of the state one.
Example: Peter earns €1,500 gross. The UPF contribution is 5% = €75: €42 (2.8%) paid by the employer and €33 (2.2%) deducted from his pay.
Watch out: Even if you never chose a company, you still have an account — check which fund you are in.
Example: Bulgaria — People born after 31.12.1959 and insured in the state "Pensions" fund are compulsorily insured in a UPF (Social Security Code, Art. 127(1)). The contribution is 5% (Art. 157). At retirement the choice is a lifetime pension, a lifetime pension with a guaranteed period, or one with phased payment of part of the money (Art. 167(4)).
Check in your country — Is part of your compulsory contribution paid into a personal fund? Your employer or your financial supervisor can tell you which one.
Source: Social Security Code (Bulgaria), Art. 127, 157, 167 (in Bulgarian) — https://lex.bg/laws/ldoc/1597824512 · FSC — https://www.fsc.bg/?page_id=21702