BTP, or Bankernas Tjänstepension (the Swedish banking industry pension fund), is an occupational pension for employees in the banking and finance sector.
Your employer decides whether to make BTP1 contributions and from which date. If an employer chooses BTP1, it will apply to staff recruited after the employer opted into the scheme and all their employees under 25.
If you are over 25 and were recruited before your employer opted into the BTP1 scheme, BTP2 contributions will continue to be made, unless you and your employer have agreed on making BTP1 contributions.