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The balance of my HSA funds is within HSA Bank, and I have a debit card for that balance. What should I do if/when that balance reaches $0? 

Close the account (tax implications if i do so/will it affect my credit score closing an account like this)?

Hold on to it if/when I get on another insurance plan and link them?

 

Currently, HSA Bank gives me the option to fund the cash-only account, so if I contribute to it without a HDHP, what are the specific implications?