Made excess 401k Roth contribution in 2024. Not knowing that, rolled contribution over in 2025. Doing taxes, got an alert that said I over contributed. How do I fix?

You do not need to amend your W-2. You also do not need to add the excess to the wages since you made the contribution to a Roth 401(k). 

To clarify, what kind of account was the financial planner account? The excess contribution part was ineligible for rollover and therefore the part allocated to the excess and earnings would be a distribution and then a new contribution to the financial planner account.

Please see Pub 525 for additional information.

Hi @DanaB27 , The excess contribution (401k Roth) was rolled over to our regular Roth. The excess contribution was with a second employer (after maxing out and retiring with the first employer...didn't realize we had already maxed out when starting with the second employer).

The rolled over 401k Roth is now sitting in a regular Roth IRA.  The financial planner is returning that excess contribution and filling out a 1099R. I believe we still need to get a corrected W-2 from that second employer, once the 1099R has been done.

This is a very complicated issue since 1. the 401k Roth was already maxed out at the previous employer (unknown to us) 2. When we started at the new employer, we didnt realize the 401k had already been maxed out, and 3. the new employer did roll over the 401K ROTH funds to our regular ROTH account with your financial planner (at our request).

Would a new employer have a way of checking to see if a previous employer 401k has been maxed out?

I keep getting different opinions from former employer, financial planner, and IRS.

Thank you for any help and insight!

No, the new employer has no way of knowing how much you contributed with a previous employer unless you tell them. 

It seems you took all the needed actions to correct this excess contribution.