Can an individual use the money in their HSA for tax dependents even if they are not covered by the accountholder's insurance plan?

Yes. HSA funds may be used to pay for qualified medical expenses for tax dependent child(ren), even if the child(ren) are not covered by the accountholder’s health insurance plan. Note: If the accountholder has individual HDHP coverage, contributions to the account are limited to the maximum for self-only coverage.