There are multiple things at play here.
* Firstly, you may have more than one HSA (the contributions limits are capped but not the number of them)
* Eligibility for withdrawing is linked to the existence of an HSA when the qualified expense occurred, whether you had the cash in the HSA or not. See the IRS notice except below.
* You can also withdraw for spouse and dependent's qualified expenses. See q36 of the same notice linked below.
At the root of your question, it seems like it's whether THE HSA from which you intend to withdraw from must have been in existence at the time of the qualified expenses versus AN HSA having to have been in existence. I believe the latter is true as I can't make sense of the burden of tracking the dollars when HSA's are merged/rolled over/receive later contributions.
These stack up in interesting ways. Suppose I had an old hsa in 2012 with $1 in it. In 2013-2015, my wife and I go on a co-pay plan and incur some qualified expenses which we paid out of pocket. Then in 2016, I (but not my wife) go back on a HDHP plan and fund an HSA. I could contribute for 2016 and then withdraw for 2013-2015 qualified expenses for my wife. That's my read and I'm pretty confident.
We've opted to max our hsa and stay fully invested and accumulate documentation supporting future withdrawals.
With regard to investing it, I'd look at whether you can do an in-service distribution/rollover. You can often avoid fees by doing a manual rollover but this is limited to once per year. That works by withdrawing a sum from the source account and depositing to the target with a rollover certification form. That will result in you getting a 5498-SA from the receiver showing the rollover. It's not as easy as the electronic rollover but trades a little paper work for savings on fees. I mention this as perhaps you could fund up the new HSA and periodically roll the HSA money over to your preferred provider.
One last thing... have you asked if you can use your own HSA provider with the new employer? Our company doesn't dictate a provider (though we make a few recommendations to employees)?
I hope this helps.
Check out
https://www.irs.gov/irb/2004-33_IRB/ar08.html, specifically question 39 excerpted below.
"Q-39. When must a distribution from an HSA be taken to pay or reimburse, on a tax-free basis, qualified medical expenses incurred in the current year?
A-39. An account beneficiary may defer to later taxable years distributions from HSAs to pay or reimburse qualified medical expenses incurred in the current year as long as the expenses were incurred after the HSA was established. Similarly, a distribution from an HSA in the current year can be used to pay or reimburse expenses incurred in any prior year as long as the expenses were incurred after the HSA was established. Thus, there is no time limit on when the distribution must occur. However, to be excludable from the account beneficiary’s gross income, he or she must keep records sufficient to later show that the distributions were exclusively to pay or reimburse qualified medical expenses, that the qualified medical expenses have not been previously paid or reimbursed from another source and that the medical expenses have not been taken as an itemized deduction in any prior taxable year. See Notice 2004-2, Q&A 31 and also Notice 2004-25, for transition relief in calendar year 2004 for reimbursement of medical expenses incurred before opening an HSA.
Example. An eligible individual contributes $1,000 to an HSA in 2004. On December 1, 2004, the individual incurs a $1,500 qualified medical expense and has a balance in his HSA of $1,025. On January 3, 2005, the individual contributes another $1,000 to the HSA, bringing the balance in the HSA to $2,025. In June, 2005, the individual receives a distribution of $1,500 to reimburse him for the $1,500 medical expense incurred in 2004. The individual can show that the $1,500 HSA distribution in 2005 is a reimbursement for a qualified medical expense that has not been previously paid or otherwise reimbursed and has not been taken as an itemized deduction. The distribution is excludable from the account beneficiary’s gross income. "
