EPSVs are the Basque equivalent of pension plans, regulated by the Provincial Councils (Diputaciones Forales) of Bizkaia, Gipuzkoa, and Álava rather than by the national rules that govern pension plans in the rest of Spain.
Main tax advantage
Contributions reduce the taxable base of regional (foral) IRPF, with an individual limit of €5,000 per year and a combined limit (personal plus employer contributions) of €10,000 from 2026, according to the rules currently in force in each historical territory.
Withdrawal
When you withdraw from an EPSV, the contributions are taxed as employment income with a 30% reduction (under the new regime from 2026), while the returns generated are taxed as investment income. Exemptions exist if withdrawn as a life annuity or after a minimum holding period.
EPSV vs. pension plan
Functionally they're very similar (finalist retirement savings with tax benefits on contributions), but the limits and the tax treatment of withdrawals can differ from national pension plans, so it's worth checking the specific regional rules for each territory.