What can be a consequence of not properly acknowledging a legal document?

Not properly acknowledging a legal document can lead to the invalidation of that document, which is why this choice is the correct one. Acknowledgment involves affirming the authenticity of signatures on a document before a notary public or other authorized official. If a document, such as a deed or contract, is not properly acknowledged, it may not hold legal weight in court, rendering it unenforceable. This can significantly impact real estate transactions by creating uncertainty over property ownership or associated rights.

The other options do not directly relate to the consequences of failing to acknowledge a legal document. Increased property value relies on market conditions and effective management rather than legal acknowledgment. Extending property tax deadlines pertains more to governmental policies and individual circumstances rather than the acknowledgment of documents. Lastly, loss of real estate equity is connected to property market values and owner behaviors, which are unrelated to how a legal document is acknowledged. Thus, the correct answer highlights the fundamental role that proper acknowledgment plays in ensuring a legal document's validity.