@Colsen28
If you bought a half interest in the house, you have nothing to report. You don't report buying assets or investments on your tax return, only when you sell (for a gain or a loss).
If you bought something worth $410,000 and only paid $400,000, then your sibling is giving you the other $10,000 of equity, you aren't giving them anything. If anyone files a gift tax return, it is your sibling, not you, but gifts less than $18,000 don't even need to be reported.
The only thing you need to do now is keep your documents related to the inheritance, the CMA, the appraisal, and so on, until you sell the home (however long that is) plus 3 years after you sell. When you sell, you will ignore the appraisal and claim an adjusted basis of $800,000. You will pay capital gains tax on any amount over that, unless you qualify for the $250,000 exclusion because you lived there as your main home at least 2 years.
