Cops say Lawrence Taylor was arrested because he had been living in a hotel for months — but failed to reveal that to law enforcement despite being required to do so.

It's all spelled out in new police documents, obtained by TMZ Sports, in which cops say the NFL legend committed a huge no-no after he failed to inform them that he had left his permanently registered address back in April.

According to the docs, officers say due to his status as a sex offender stemming from a 2011 conviction, Taylor must be diligent any time he moves and notify authorities of the change of address.