you have to add him as a dependent assuming he qualifies.
the child must
1) be the taxpayer's child, stepchild, eligible foster child or descendant of any of them such as a grandchild or brother, sister half-brother, half-sister, stepbrother, stepsister or descendant of any of them such as a niece or nephew, legally adopted child or place with the taxpayer for legal adoption
2) be any of the following a) under age 19 at the end of the year b) a full-time student and under age 24 at end of the year c) or any age if totally and permanently disabled
3) have the same principal abode as you for more than ½ the tax year. (spends more than 182 nights in your abode)
4) grandson hasn’t provided over ½ his support
5) No joint return with the exception for a joint return filed only to claim a refund of tax withheld when neither spouse is required to file and no tax liability would exist for either spouse if separate returns were filed
just a warning. there is no way to stop his parents (where i assume he spends the weekends from also claiming him) if they do and efile before you, you will not be able to efile. you'll have to mail in your return.
