You must have misunderstood. The IRS will never audit for NOT claiming HOH - they will audit if you DO claim HOH and are not entitled to do so.
Unless the parents claim the rent as rental income on a schedule E on the parents tax return then the "rent" you pay them is probably just sharing expenses and not actual rent especially if the "rent" is less than you would pay on the open market from a unrelated landlord. If that is the case then it is the parents household and you and BF are part of their household.
Now it is possible to have separate households under one roof, but the IRS requires that the households are indeed separate.
Note that calming HOH requires that you pay MORE than half the keeping of the entire household and that includes all household expenses including food of everyone in that household. If the parents supply the food and you all eat together then you might have a hard time convincing the IRS that the households are indeed separate.
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
