The main difference between a designated member and a regular member in an LLP lies in the level of legal responsibilities and obligations they have within the partnership.

A designated member is a specific role within an LLP that carries additional responsibilities and legal obligations compared to regular members. Designated members have specific duties and are responsible for ensuring that the LLP meets its legal obligations, such as filing accounts and annual returns with the relevant authorities. They also have the authority to make decisions on behalf of the LLP and have the power to bind the partnership.

Regular members are individuals who have a stake in the LLP, but do not have the same level of legal responsibilities as designated members. They are not required to carry out specific duties or have the same decision-making powers as designated members. Regular members may still have voting rights and be entitled to a share of the profits, but they do not have the same level of legal accountability. It is important to note that all designated members are also regular members, but not all regular members are designated members. 

There is a minimum requirement of at least two designated members to form a LLP.