Return was reject - someone else claimed our foster children, & shouldn't have. We now have to file via paper. Do we have to mail all documentation in as of 4/15?

Hi there-

Yes tax returns are due on April 15th- this also includes any payment for tax due- this means they must be postmarked by April 15th.

If you need additional time to gather documentation and prepare you can always file an extension. 

TurboTax has a site that easily prepares extensions https://turbotax.intuit.com/irs-tax-extensions/