TL;DR: You must express your renunciation to the judicial court within whose jurisdiction the succession was opened. Renunciation means that you are considered never to have been an heir and releases you from the debts and charges of the estate. However, you must comply with the rules relating to deadlines and the formal demand.
Where to Make Your Renunciation
Renunciation is not presumed from your conduct. To make it enforceable against third parties, you must make it to the judicial court within whose jurisdiction the succession was opened.
This rule concerns renunciation exercised by a universal heir or an heir entitled to a universal share.
What Are the Effects of Renunciation?
You are considered never to have been an heir. You are therefore not liable for payment of the debts and charges of the estate.
Your renunciation does not necessarily cause your share of the estate to disappear. In successions devolving in the direct or collateral line, your descendants may represent you. In the absence of representatives, your share passes to your co-heirs or, if you are the sole heir, to the next degree.
What Deadlines Must You Comply With?
You cannot be compelled to exercise your succession option before the expiry of a period of four months from the opening of the succession.
In the absence of a formal demand and if you have not performed an act as an heir, you may exercise your succession option for ten years. At the end of this period, you are deemed to have renounced the succession.
The formal demand asks you to take a position on the succession. Within the following two months, you must make your choice or request additional time from the judge if you have been unable to complete the inventory you began or if you can establish a serious and legitimate reason.
If you do not respond within the applicable period, you are deemed to have accepted the succession outright. You may also withdraw as part of the formal demand: this withdrawal is equivalent to an outright acceptance.
What Happens to Your Share?
The share that would have been allocated to you may pass to your representatives. In their absence, it accrues to your co-heirs. If you are the sole heir, it devolves to the next degree.
Can You Revoke Your Renunciation?
You may revoke your renunciation by accepting the succession outright as long as the limitation period for the right to accept has not run against you.
This revocation is possible only if no other heir has already accepted the succession and if the State has not already been sent into possession. The acceptance then produces retroactive effect as of the day the succession was opened.