Can an employer limit an employee's pre-tax monthly contribution to HSA ? (provided that the employee has full year HDHP coverage and still under annual HSA limit?)

[TaxGuyBill]

Yes, they can.

As I said before, pay for the medical out-of-pocket now.  In December (after your employer contributions have built up), withdraw that amount from your HSA and everything will work out.

[Critter]

I agree with Bill ...  If you don't want to wait until there in money in the HSA to pay the medical bill then just pay it out of pocket and then reimburse yourself with the HSA distribution later.    Or wait until the money is in the HSA and take a distribution to pay the medical bill later.  It is the exact same thing and you are not loosing anything.  Stop focusing on what you cannot change and work with the tools you have.  Life it too short to stress this much and you are lucky you do have this HSA to use and save tax money, not all folks are so fortunate.

[dmertz]

You can reimburse yourself with a distribution from your HSA at any time in the future for medical expenses incurred after the establishment of your HSA and were originally paid out of pocket.  As others have said, since you already have a HSA account, pay the medical expense out of pocket and at some later date when there are sufficient funds in the HSA, take a distribution from the HSA to reimburse yourself for those expenses.  Just be sure to retain receipts for the medical expenses in case the IRS questions that your HSA distributions were actually used for qualified medical expenses.