Level 15

Education

This is basically answered in your other post at <a rel="nofollow" target="_blank" href="https://ttlc.intuit.com/questions/4514117">https://ttlc.intuit.com/questions/4514117</a>  
You can withdraw money from your 529 at any time, for any reason, in any amount. The employer tuition reimbursement has nothing to do with this, and is completely separate and irrelevant. Any and all 529 funds not used for qualified education expenses is the same tax year they are withdrawn, will be taxable income to the beneficiary recipient of those funds.