With just one month left in the two-year legislative session, a group of lawmakers this week introduced a union-backed proposal that would impose a large, retroactive personal income tax increase on income over $1 million (AB 1253, Santiago). Senator Mike McGuire, chair of the Senate Governance and Finance Committee, announced that the committee will hold an August 3 testimony-only hearing on the bill. CalTax opposes AB 1253, noting that California already has the highest-in-the-nation top tax rate of 13.3 percent,…