Luma tax will use the money to build out software that makes it easier for small businesses to file and pay sales taxes. LumaTax, formerly known as SALTSolver, is starting with California small businesses. LumaTax’s app lets businesses create exemption certificates, which are needed when businesses sell to one another, for passing along the responsibility for collecting sales tax. LumaTax also plans to offer California-based small businesses a cloud service to file their sales tax returns.