Section 464 of the Companies Act, 2013 stipulates that a partnership firm may have up to 50 partners, provided it is not registered as a company. With the current firm having 45 partners against the maximum limit of 50, the calculation for additional partners is as follows: \[ \text{Remaining partners that can be admitted} = 50 - 45 = 5 \]. Consequently, the partnership firm can admit 5 additional partners.