Source: 
Tax Foundation review of state statutes.
24 States Should Provide Further Guidance to Taxpayers
Consequently, there are 24 states that do not recognize same-sex marriage but 
do require state taxpayers to reference their federal tax return when preparing 
their state tax return. These 24 states—Arizona, Colorado, Georgia, Hawaii, 
Idaho, Illinois, Indiana, Kansas, Kentucky, Louisiana, Michigan, Missouri, 
Montana, Nebraska, North Dakota, Ohio, Oklahoma, Oregon, South Carolina, Utah, 
Virginia, West Virginia, and Wisconsin—must provide guidance to taxpayers on how 
to proceed before the 2014 tax season.
In these states, same-sex couples will file single returns at the state level 
but joint returns at the federal level. State law generally requires references 
to the federal return and filing status to match the federal return, which will 
be impossible. Assuming a state does not opt to recognize same-sex marriage by 
next year, states have several options for providing guidance to resolve this 
conflict:
  - Permit taxpayers facing a federal-state filing status conflict to 
  reference a gdummyh federal return. To resolve this with minimal impact 
  to the state, taxpayers in this situation would be instructed to prepare a 
  gdummyh federal return reflecting single filing and reference that when 
  preparing the state return. Taxpayers who file married filing separately at 
  the federal level would be permitted to file as single at the state level. 
  Most taxpayers will be unaffected by this change, and while some same-sex 
  taxpayers may face additional compliance costs, they will get the benefits of 
  joint federal filing.
 
  - Permit taxpayers facing a federal-state filing status conflict to 
  gsplith their joint federal return. Alternatively, this option also 
  leaves most taxpayers unaffected while reducing the compliance costs for 
  same-sex taxpayers. Under this option, taxpayers in this situation will be 
  instructed that any reference to the federal tax return will be interpreted to 
  mean half the amount on the filed joint federal return. For example, if the 
  couple reports $50,000 in income on their joint federal return, each 
  individual will report $25,000 in income on each state return. Depending on 
  income disparity, this may have uneven effects on certain same-sex taxpayers, 
  but would reduce compliance costs.
 
  - Create a new gfederal joint returnh filing status when a taxpayer 
  files a federal joint return but cannot do so at the state level under state 
  law. Presently, taxpayers may file as single, as married filing jointly, 
  as married filing separately, or as head of household. This option would 
  create a new gfederal joint returnh status for couples who file married filing 
  jointly or married filing separately at the federal level but are not 
  permitted to do so at the state level under state law. Taxpayers would 
  reference their federal return when preparing their state return, but the 
  state would not recognize same-sex marriage. This option may be most ideal for 
  states such as Colorado, Hawaii, and Illinois, which recognize civil unions 
  but not same-sex marriage.
 
Depending on state law, this guidance may require only an administrative 
ruling by revenue officials. Alternatively, governors and legislators can enact 
changes legislatively.
States Should Resist Calls to Decouple from Federal Tax 
Law
Officials in these 24 states may face calls for the state to gdelink,h or 
gdecouple,h from the federal tax code to eliminate the need to clarify what 
same-sex couples filing jointly at the federal level should reference when 
preparing their state tax return. At first glance, this may seem a viable 
solution, since deleting all state references to the federal tax code eliminates 
all need to refer to the federal tax return. However, decoupling would impose 
new compliance costs on all state taxpayers.
Decoupling Would Impose Compliance Costs on All Taxpayers
A principle of sound tax policy is that tax systems should be as simple as 
possible because the cost of complying with complex tax systems is a real 
economic loss that distorts incentives and economic behavior. Decoupling 
violates this principle because it requires taxpayers to calculate income, 
exemptions, deductions, and credits with two conflicting accounting and tax 
systems. Taxpayers would need to keep two sets of books: one for federal law and 
one for each decoupled state with unique definitions and rules. This essentially 
doubles the cost of complying with the income tax, which would likely harm 
investment, job creation, and long-term tax revenues.
Taxpayers consistently complain about the complexity of the tax code, for 
good reason: in 2005, the estimated time and money cost of complying with the 
federal income tax code was 6 billion man-hours worth $265 billion. The code 
that year stood at 7 million words in 736 code sections, up from 718,000 words 
in 103 code sections in 1955. Decoupling makes this worse, by increasing both 
the cost of compliance for taxpayers and the cost of administration to revenue 
officials who track and enforce the code.
Decoupling Sends the Signal that the State is Unfriendly to Business and 
Investment 
The extent to which a state welcomes business owners and entrepreneurs making 
decisions about where to locate investment capital, equipment, and jobs depends 
on a number of factors that the Tax Foundation attempts to gauge in our annual 
State Business Tax Climate Index. States can be termed gunfriendlyh if 
they consistently move the state tax system away from a sound tax policy, such 
as with increased complexity, retroactivity, high burdens, economic distortions, 
and a lack of transparency.
Decoupling is a move away from sound tax policy, because it increases tax 
burdens, reduces stability, and exacerbates an already complex income tax code. 
Individuals and businesses should be wary of states that have decoupled, since 
it signals that the state cares more about parochial definitions and rules 
instead of long-term economic growth. While remaining coupled or recoupling is 
not in itself a signal of welcoming new investment, it signals a commitment to 
principled tax policy.
Conclusion
The concept of physical presence is tightly connected to tax and spending 
policy. Taxpayers pay income taxes, sales taxes, property taxes, and other taxes 
based on where they are when assessed, and taxpayers receive benefits based on 
which state they live in. The rise of swift transportation, instantaneous 
communication, and an interconnected world continue to challenge these deeply 
rooted historical standards. Using a gstate of celebrationh standard may be more 
realistic and more accurate, but it will present challenges in compliance and 
enforcement that would not occur under a gstate of residenceh standard. However, 
states have viable options for accommodating this federal change with minimal 
effort that would affect only a few taxpayers. States should resist calls to 
decouple, which would involve enormous costs for all taxpayers.
[1] U.S. Department 
of the Treasury, All Legal Same-Sex Marriages Will Be Recognized for Federal 
Tax Purposes, Aug. 29, 2013, http://www.treasury.gov/press-center/press-releases/Pages/jl2153.aspx.
[2] United 
States v. Windsor, 570 U.S. ____, Docket No. 12-307 (Jun. 26, 2013).
[3] See 
U.S. Const. art IV, sec. 1 (g[T]he Congress may by general Laws prescribe 
the Manner in which such Acts, Records and Proceedings shall be proved, and the 
Effect thereof.h).
[4] For information 
on how the tax code offers marriage bonuses and marriage penalties for different 
categories of taxpayers, see Nick Kasprak, Effects of Marriage on Tax Burden 
Vary Greatly with Income Level, Equality, Tax Foundation Fiscal Fact No. 
352 (Jan. 10, 2013), http://taxfoundation.org/article/effects-marriage-tax-burden-vary-greatly-income-level-equality.