What the notice is for
A pay-or-quit notice is the document that starts the formal eviction process for nonpayment of rent. It tells you exactly how much you owe and gives you a fixed window to pay it in full. If you pay everything demanded within that window, the notice is satisfied and the landlord generally can't proceed to file an eviction lawsuit based on that missed payment. If you don't pay and don't move out, the landlord's next step is filing in court.
What the notice legally has to say
To be valid, this kind of notice generally has to be in writing, state the specific dollar amount owed, and give a defined deadline. California's unlawful detainer statute is a useful concrete example of how detailed these requirements can get: it requires the notice to demand payment of the rent due, state the amount, and include the name, phone number, and address of the person to whom payment should be made, with three days (excluding weekends and judicial holidays) to pay before the landlord can act further (Cal. Code Civ. Proc. § 1161(2)). Other states set different deadlines and requirements, so the exact number of days and the exact content required is a question for your own state's law, not a fixed national standard.
How the notice has to reach you
States also regulate how the notice can be delivered, and getting this wrong can make an otherwise-valid notice void. California, again as one example, allows delivery by handing it to you personally, or — if you're not reasonably available — leaving it with someone else at your home or workplace and also mailing a copy, or, as a last resort, posting it in a conspicuous place and mailing a copy (Cal. Code Civ. Proc. § 1162). If the way you were actually served doesn't match what your state requires, that can be a real defense if the case proceeds to court.
Errors in the notice matter
A notice that gets the amount wrong, sets an unclear or too-short deadline, or is delivered improperly can be challenged as defective. That doesn't mean you should ignore a notice hoping to find an error later — verify the amount immediately and act within the deadline as if the notice is valid, while also keeping careful notes on exactly how and when it was delivered to you, in case a defect does turn up.
What counts as "paying" during the window
Generally, you need to pay the full amount stated, not a partial payment, to fully satisfy the notice, though state rules on partial payment vary and some states treat accepting any partial payment as resetting the process. If you dispute part of the amount — say, a late fee you believe is miscalculated — paying the undisputed rent itself while raising the fee dispute separately is usually the safer path, since falling short on the total demanded can leave the notice unsatisfied even if your dispute over part of it is legitimate.
A concrete example
Say you owe $1,750 in back rent and your landlord serves a written notice demanding that amount with a specific number of days to pay, as required under your state's law. If you pay the full $1,750 by that date and get a receipt, the notice is satisfied and the landlord generally has no basis to proceed with an eviction over that missed payment. If the deadline passes without full payment, the landlord's next move is filing an eviction lawsuit, at which point how long does the eviction process take is worth reading for what comes next.
What to do if you get one
Read it immediately and check the amount against your own records. If you can pay, do it before the deadline and keep proof — a receipt, a bank transfer confirmation, anything dated. If you can't pay in full, contact a local rental assistance program right away, since many can pay a landlord directly and quickly enough to beat the deadline, and talk to a legal aid organization about your options before the window closes.