The Social Security Administration (SSA) announced that the Social Security wage base is increasing in 2018, but not by much. It says the 6.2% Social Security tax will apply to $128,700 of wages in 2018, up from $127,200 in 2017. That’s an increase of slightly more than 1% as compared with the increase of more than 7% the prior year. The 1.45% HI (Hospital Insurance) tax still applies to all wages.