Form 1095-A - Shared Allocation
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“If an individual in your tax family was enrolled in a policy with an individual in another tax family and you are not taking the PTC, the taxpayer who is claiming the individual not in your tax family may agree to reconcile all APTC paid for the policy.”
For more information, refer to the examples in the instructions for Form 8962.

To enter shared allocation, follow the instructions in FAQ Form 1095-A - Entering Health Insurance Marketplace Statement in Program. You will be prompted to allocate amounts during the interview process.