1. A method for optimizing recategorization of financial transactions using collaborative filtering, comprising: obtaining a plurality of historical financial transactions of a plurality of users with a merchant, each of the plurality of historical financial transactions comprising user identification for one of the plurality of users, a merchant name of the merchant, an initial category assigned to each of the plurality of historical financial transactions, and a recategorization value of a plurality of recategorization values for each of the plurality of historical financial transactions, wherein the plurality of historical financial transactions occurred in the past; determining, using a processor, a first portion of the plurality of historical financial transactions assigned to each recategorization value of the plurality of recategorization values; determining, using the processor, a second portion of the plurality of historical financial transactions where the each recategorization value is different from the initial category; generating, using the processor, a recategorization index for the each recategorization value using: RI i = count ⁡ ( RC i ) count ⁡ ( all ⁢ ⁢ RC ⁢ ⁢ where ⁢ ⁢ RC != C ⁢ ⁢ 1 ⁢ ⁢ and ⁢ ⁢ RC != null ) , wherein RI i is the recategorization index, RC i is the first portion of the plurality of historical financial transactions, RC is the plurality of recategorization values, and C1 is the initial category assigned to each of the plurality of historical financial transactions; determining, using the processor, an alternative categorization candidate based on the recategorization index of the each recategorization value; assigning, based on the recategorization index exceeding a threshold, the alternative categorization candidate as a new initial category for a plurality of future financial transactions with the merchant; and maintaining the initial category assigned to each of the plurality of historical financial transactions.