In 2018, our 22 year old son got married, was a full time student and made around 40,000 but we provided more than half of his support. He lived with us for 7 months of the year. We are claiming him as a dependent. He and his wife (who had no income in 18) are filing "married filing jointly". They are only filing to get a refund of taxes withheld. TT won't allow us to transmit the efile. I have run the IRS' own "Whom may I claim as a dependent" online tool and it says we can claim him.