A notice of entry is the advance written notice a landlord gives a tenant before entering an occupied unit, stating when the entry will happen and why. Most states require it for routine reasons like repairs, inspections, or showings, and the lead time is commonly in the 24 to 48 hour range, though the exact count and the list of valid reasons live in your state's statute.
In practice
Say a tenant reports a leaking kitchen faucet on a Monday and you want to send a plumber on Wednesday morning. If your state uses a 24-hour standard, a written notice delivered Tuesday morning that names the Wednesday 9 a.m. to noon window and the reason, faucet repair, clears the requirement with room to spare. If your state uses 48 hours, that same Tuesday-morning notice falls short for a Wednesday-morning visit: you would either push the appointment to Thursday or get the tenant's written consent to come sooner.
The two variables that decide compliance are the lead time and how you count it. A 24-hour rule measured in calendar hours is different from one measured in business days, and a notice slipped under the door at 8 p.m. may not start the clock until the next morning under some statutes. Genuine emergencies, a burst pipe or a fire, are the usual exception and let you enter without notice, but a leaky faucet two days out is not an emergency.
Why it matters to a small landlord
Entry is where a landlord's right to maintain the property runs straight into the tenant's right to be left alone, and skipping the notice is one of the fastest ways to hand a tenant a real grievance. A pattern of entering without notice can rise to a breach of the tenant's quiet enjoyment, which becomes ammunition in a dispute and, in extreme cases, a defense against you. The fix is dull and effective: send the notice every time, in writing, even when the tenant says it is fine, and keep a copy. If you manage from another city, build the habit into how you manage a rental remotely so a contractor never shows up at a door the tenant was not warned about.
Notice of entry sits next to the other moments when access and documentation overlap. The move-in inspection is a scheduled entry you both expect, the make-ready period between tenants is the one window when the unit is yours to enter freely, and everything in between runs on written notice and a tenant's quiet enjoyment. Treat the notice as routine and the access problem mostly disappears.