I just realized that I could add my father-in-law as a dependent. He ahs been living with us for 11 1/2 months in 2018 and we have been paying for his living expenses.
technically you don't qualify. the rule for qualifying relative is that they lived in taxpayers household for the ENTIRE year except for temporary absences. such as hospitalization. 11-1/2 is NOT an entire year so hopefully that 1/2 month was a temporary absence.
From Pub 501:
Member of Household or Relationship Test
To meet this test, a person must either:
1. Live with you all year as a member of your household, or
2. Be related to you in one of the ways listed under Relatives who don't have to live with you.
Relatives who don't have to live with you. A person related to you in any of the following ways doesn't have to live with you all year as a member of your household to meet this test:
• Your son-in-law, daughter-in-law, father-in-law, mother-in-law, brother-in-law,
Any of these relationships that were established by marriage aren't ended by death or divorce.
An in-law is closely related so there is no requirement that he live with you at any time, during the year. But if you provided a home it helps your support case, unless they own the home you live in. If no one person (or married couple) provides 50% of the support (for example your siblings are also sending support), then a "multiple support agreement” (IRS Form 2120) can be used, to allow you to claim the dependent. <a rel="nofollow" target="_blank" href="https://www.irs.gov/pub/irs-pdf/f2120.pdf">https://www.irs.gov/pub/irs-pdf/f2120.pdf</a>
The IRS has a worksheet that can be used to help with the support calculation. See: <a rel="nofollow" target="_blank" href="http://apps.irs.gov/app/vita/content/globalmedia/teacher/worksheet_for_determining_support_4012.pdf"...> The support value of a home is the fair market rental value, divided by the number of occupants.