Great question. Under § 38-22-109(3) of the Colorado lien statute
, Notice of Intent to Lien must be sent to the owner or reputed owner, or their agent, at least 10 days prior to the filing of a lien statement. That notice must be served by personal service or registered or certified mail, return receipt requested, and it must be sent to the last known address of the party being served. For proof that this was done, at the time of filing a Colorado mechanics lien, an affidavit must be filed, along with the lien, stating that the service or mailing was made at least 10 days before the lien was filed. So, as long as the Notice of Intent to Lien was sent as required (certified mail, return receipt requested - or by personal service) to the party required (i.e. the owner, reputed owner, or their agent) to the address required (that party's last known address), then a claimant is able to submit a truthful affidavit saying that service was made - as long as that occurred at least 10 days prior to the filing of the lien claim. For more on Colorado lien and notice rules, this resource should be helpful: Colorado Lien & Notice FAQs
. For more on Colorado's Notice of Intent to Lien specifically, this post should be helpful: What is a Colorado Notice of Intent to Lien?