The ACA has been modified at least five times since being passed by Congress.
All quotes of the Patient Protection and Affordable Care Act will be from govtrack.us.
-Delay of the out-of-pocket costs: The limit on out-of-pocket costs was not supposed to exceed $6,350 for an individual and $12,700 for a family in 2014. That section requirement was waved for some insurance companies, allowing them to set higher limits or no limits on some costs in 2014.
"(A) 2014- The cost-sharing incurred under a health plan with respect to self-only coverage or coverage other than self-only coverage for a plan year beginning in 2014 shall not exceed the dollar amounts in effect under section 223(c)(2)(A)(ii) of the Internal Revenue Code of 1986 for self-only and family coverage, respectively, for taxable years beginning in 2014." --ACA Section 1302(c)(1)(A)
-Delay of the employer mandate: This is extensively covered in this question, so I won't rehash it here.
(1) REPORTING BY EMPLOYERS- Section 1514(d) of the Patient Protection and Affordable Care Act is amended by striking 'December 31, 2013' and inserting 'December 31, 2014'.
(2) REPORTING BY INSURANCE PROVIDERS- Section 1502(e) of the Patient Protection and Affordable Care Act is amended by striking '2013' and inserting '2014'.
-Subsidies for Congress & staff on the exchanges: The Office of Management and Budget offered a 75% subsidy for Congress and their staff on the health care exchanges. Previously, they had a portion of their premiums paid under their old health care plan, the Federal Employee Health Benefits program. At issue, is the fact that the OMB doesn't have the power to appropriate funds Congress hasn't authorized.
"(i) REQUIREMENT- Notwithstanding any other provision of law, after the effective date of this subtitle, the only health plans that the Federal Government may make available to Members of Congress and congressional staff with respect to their service as a Member of Congress or congressional staff shall be health plans that are--"
"(I) created under this Act (or an amendment made by this Act); or"
"(II) offered through an Exchange established under this Act (or an amendment made by this Act)."--ACA Section 1312(d)(3)(D)(i)
The IRS replaces household income with employee W-2 wages: Employers were deeply concerned with this provision of the law, since they usually aren't privy to household income, only what they pay there employees. This and other ACA rewrites are the basis of a lawsuit in federal court, the details of which are not within the scope of this question.
"36B(c)(2)(C)(i) the employee’s required contribution (within the meaning of section 5000A(e)(1)(B)) with respect to the plan exceeds 9.8 percent of the applicable taxpayer’s household income."--ACA Section 1401(a)
The IRS makes subsidies available in federally run exchanges: The proposed regulation makes available premium subsidies in 1321 (federal exchanges), when they are only available in 1311 (state exchanges).
"36B(b)(2) the monthly premiums for such month for 1 or more qualified health plans offered in the individual market within a State which cover the taxpayer, the taxpayer’s spouse, or any dependent (as defined in section 152) of the taxpayer and which were enrolled in through an Exchange established by the State under 1311 of the Patient Protection and Affordable Care Act, or [...]"--ACA Section 1401(a)