For easy reference, here are some charts of useful limits, thresholds and other handy figures you may need for 2018. 

Other years:  2017  |  2019

ACA Market Reforms & Employer Shared Responsibility
Plan-year OOPM limit (see note 1) Individual $7,350
Family $14,700
Maximum fixed-dollar cost sharing increase from March 23, 2010 For changes effective January 1, 2018 38.177% (see note 2)
PCORI fee due July 31 For plan years ending October 1, 2017 through December 31, 2017 $2.39/covered life
For plan years ending January 1, 2017 through September 30, 2017 $2.26/covered life
Employer shared responsibility (pay-or-play) affordability threshold 9.56%
Note 1: No one covered person with family coverage can be required to exceed the individual ACA OOPM limit. Also, OOPM limit is effective for plan year beginning on or after January 1 of the indicated year.
Note 2: This figure is current as of October 20, 2017. The inflationary index for maximum permitted changes to grandfathered health plans is tied to data published by the Bureau of Labor Statistics after the start of the plan year to which it relates—that is, long after plan designs are established. This table is updated periodically to reflect the highest permissible change for grandfathered plans known at the time of publication.

Health Savings Accounts (HSA)
Calendar-year contribution limit Individual $3,450
Family $6,850
Minimum HSA-qualified HDHP deductible Individual $1,350
Family $2,700
HSA-qualified HDHP OOPM limit Individual $6,650
Family $13,300
Note: HSA-qualified HDHP OOPM limit is different than a similar ACA market reforms OOPM limit. Also, HDHP deductible minimum and OOPM limit amounts apply to first plan year beginning on or after January 1 of the indicated year.

Healthcare Flexible Spending Arrangements (FSA)
Salary reduction limit $2,650

Dependent Care Assistance Programs (DCAP)
Salary reduction/benefit limit for single or married, filing jointly $5,000
Salary reduction/benefit limit for married, filing separately $2,500

Nondiscrimination Testing
Prior-year HCE compensation threshold Applies to 125 pre-tax premium, FSA, HSA, DCAP $120,000
Prior-year key employee officer compensation threshold Applies to 125 pre-tax premium, FSA, HSA, DCAP $175,000
Prior-year key employee more-than-1% owner compensation threshold Applies to 125 pre-tax premium, FSA, HSA, DCAP $150,000
Current-year HCI compensation threshold Applies to FSA, self-insured medical, HRA Top-paid 25%
Note: HCIs also include more-than-10% owners and the top-paid 5 officers, but these individuals usually are also included in the top-paid 25%.

Qualified Transportation Fringe Benefits
Monthly limit for parking benefit $260
Monthly limit for transit passes and vanpooling expenses $260

Adoption Assistance
Annual income exclusion limit $13,810
Annual tax credit limit $13,810
Income exclusion and tax credit phase-out range Phase-out begins at MAGI of $207,140; income exclusion and tax credit unavailable at $247,140 or higher