Issue with Maxing 401k for 2015

[AlexAG]

For my 401k the contributions don't actually show up for a couple weeks after the corresponding paycheck.  The 401k is actually through Vanguard and the transaction date is between 5-10 days after the payday. If I get paid on December 31 this year but the contributions don't post until January would those contributions count against this year's limit or next?

[dandarc]

This year.  They withheld the money out of a check paid this year.

You could also ask your HR to be sure.

[Vilgan]

This year.  They withheld the money out of a check paid this year.

You could also ask your HR to be sure.

This.

The IRS looks at the pay stub and what is reported by your employer, not at when money arrives at the 401k.