Your call. He cannot claim her if you file jointly. If you file separately you will probably pay more tax.
IF she qualifies as his dependent.
====
---Tests to be a Qualifying Relative (& Unrelated Persons)---
(Must meet ALL of these tests to be a dependent)
1. The person cannot be your qualifying child or the qualifying child of any other taxpayer.
2. The person either must be related to you, or must live with you all year (all 365 days - There are exceptions for temporary absences such as school, illness, business, vacation, military service) as a member of your household.
3. The person's gross income for the year must be less than $4,150 (tax-exempt income, such as certain social security benefits, is not included in gross income)
4. You must provide more than half of the person's total support** for the year.
5. The person is not filing a joint return.
In any case, the person must be a U.S. citizen, U.S. resident alien, U.S. national, or a resident of Canada or Mexico
The above is simplified; see IRS Publication 17, for full information.
https://www.irs.gov/publications/p17#en_US_2017_publink1000170933
** Worksheet for determining support
https://www.irs.gov/publications/p17#en_US_2017_publink1000171012
=====
---Tests To Be a Qualifying Child---
(Must pass ALL of these tests)
NOTE: If a child passes all of these tests he must say “yes” on his/her own tax return (if he/she files one) that another taxpayer CAN claim him/her as a dependent even if they DO NOT claim him/her)
1. The child must be your son, daughter, stepchild, foster child, brother, sister, half brother, half sister, stepbrother,stepsister, or a descendant of any of them.
2. The child must be (a) under age 19 at the end of 2018, (b) under age 24 at the end of 2018 and a full-time student* for any part of 5 months of 2018, or (c) any age if permanently and totally disabled and must be younger than you (or your spouse if filing jointly).
3. The child must have lived with you for more than half of the year (There are exceptions for temporary absences such as school, illness, business, vacation, military service).
4. The child must not have provided more than half of his or her own support for the year.
See Worksheet 3-1. Worksheet for Determining Support
https://www.irs.gov/publications/p17#en_US_2017_publink1000171012
5. If the child meets the rules to be a qualifying child of more than one person, you must be the person entitled to claim the child as a qualifying child.
6. The child is not filing a joint return.
7. The child must be a U.S. citizen, U.S. resident alien, U.S. national, or a resident of Canada or Mexico
*A full-time student is a student who is enrolled for the number of hours or courses the school considers to be full-time attendance during some part of each of any 5 calendar months of the year.
See IRS Publication 17 for more information.
https://www.irs.gov/publications/p17#en_US_2017_publink1000170876
Your call. He cannot claim her if you file jointly. If you file separately you will probably pay more tax.
IF she qualifies as his dependent.
====
---Tests to be a Qualifying Relative (& Unrelated Persons)---
(Must meet ALL of these tests to be a dependent)
1. The person cannot be your qualifying child or the qualifying child of any other taxpayer.
2. The person either must be related to you, or must live with you all year (all 365 days - There are exceptions for temporary absences such as school, illness, business, vacation, military service) as a member of your household.
3. The person's gross income for the year must be less than $4,150 (tax-exempt income, such as certain social security benefits, is not included in gross income)
4. You must provide more than half of the person's total support** for the year.
5. The person is not filing a joint return.
In any case, the person must be a U.S. citizen, U.S. resident alien, U.S. national, or a resident of Canada or Mexico
The above is simplified; see IRS Publication 17, for full information.
https://www.irs.gov/publications/p17#en_US_2017_publink1000170933
** Worksheet for determining support
https://www.irs.gov/publications/p17#en_US_2017_publink1000171012
=====
---Tests To Be a Qualifying Child---
(Must pass ALL of these tests)
NOTE: If a child passes all of these tests he must say “yes” on his/her own tax return (if he/she files one) that another taxpayer CAN claim him/her as a dependent even if they DO NOT claim him/her)
1. The child must be your son, daughter, stepchild, foster child, brother, sister, half brother, half sister, stepbrother,stepsister, or a descendant of any of them.
2. The child must be (a) under age 19 at the end of 2018, (b) under age 24 at the end of 2018 and a full-time student* for any part of 5 months of 2018, or (c) any age if permanently and totally disabled and must be younger than you (or your spouse if filing jointly).
3. The child must have lived with you for more than half of the year (There are exceptions for temporary absences such as school, illness, business, vacation, military service).
4. The child must not have provided more than half of his or her own support for the year.
See Worksheet 3-1. Worksheet for Determining Support
https://www.irs.gov/publications/p17#en_US_2017_publink1000171012
5. If the child meets the rules to be a qualifying child of more than one person, you must be the person entitled to claim the child as a qualifying child.
6. The child is not filing a joint return.
7. The child must be a U.S. citizen, U.S. resident alien, U.S. national, or a resident of Canada or Mexico
*A full-time student is a student who is enrolled for the number of hours or courses the school considers to be full-time attendance during some part of each of any 5 calendar months of the year.
See IRS Publication 17 for more information.
https://www.irs.gov/publications/p17#en_US_2017_publink1000170876