Q: wanting to know if I have to sign this new 872 since last was incorrect

A: The IRS often offers people the ability to pursue an Appeal of initial audit finding before the IRS issues a Statutory Notice of Deficiency. However, Appeals will only accept the case if they have at least 395 days before the current Statute of Limitations on Assessment is set to expire; this is intended to allow time for Appeals to have someone assigned and consider the issues before they need to issue the Notice of Deficiency so that they can avoid losing the ability to assess taxes while the case is pending assignment to an Appeals Officer. If you refuse to sign the 872 consenting to an extension of the Statute of Limitation on Assessment, the examiner will not send the case to Appeals and will instead issue a Notice of Deficiency. Once that Notice of Deficiency is issued, you will have 90 days to petition Tax Court to contest the assessment. If you petition Tax Court and your case has not already gone to Appeals, after IRS Counsel files an Answer to your Petition they will typically send the case back to Appeals to consider your objections to the assessment before proceeding to an actual trial in Tax Court.

If you don't contest the case in Tax Court and the assessment becomes final, then your only way to challenge it is through an Audit Reconsideration request or after payment through a Refund request.

If your representative is not an attorney and has not taken the Tax Court Bar to be able to represent people in Tax Court, then they are likely saying your only way to challenge the assessment would be through an audit reconsideration because they would not be able to represent you in a challenge to the assessment in Tax Court and you would either need to hire someone else or represent yourself.