Give the scheduler three things and nothing else: the limit, the date it starts, and whether it ends. Oregon shows what a written limit looks like in practice — covered retail, hospitality and food services employers with 500 or more employees worldwide must give a new employee a written good faith estimate of the median hours expected in an average month, and must post the schedule in writing at least 14 calendar days before its first day (Oregon BOLI). The reason you can keep the rest to yourself is equally concrete: the EEOC's enforcement guidance says an employer shall not make disability-related inquiries of an employee unless the inquiry is "job-related and consistent with business necessity" (EEOC).
Three kinds of availability, three different messages
"I cannot work evenings" does not say whether that means this month or forever, and "I might be able to help" does not say what has to happen first. Sort your request into one of three shapes before writing it, then send only that shape.
Scroll sideways to see the full table →
| Message | What you state | What closes it |
|---|---|---|
| Fixed limit | The latest finish or unavailable window, and the roster it starts with | A confirmation in the scheduling system |
| Temporary limit | The same limit plus a start date and an end date | The end date, after which the old pattern resumes |
| Conditional offer | The shift you could take and the single condition | The condition confirmed, in writing, before you accept |
The difference matters to the roster, not to your privacy. A temporary limit with no end date becomes a permanent one in the scheduler's file, and a conditional offer without its condition becomes an acceptance in the manager's memory.
Write the limit the scheduler can record
Use clock times and calendar dates. "Available Tuesday" can mean a start at any hour of Tuesday; "any shift that ends by 4 pm on Tuesdays, from the October roster" can be typed into a system. Say which roster it begins with, because Oregon's 14-day posting rule shows why timing is the whole game: a request that arrives after the schedule is written costs someone a change, and in Oregon a covered employer that changes the date, start time or end time of a posted shift owes one hour at the regular rate in addition to wages earned (Oregon BOLI). Sending the request before the roster is drawn is the cheapest version of the same conversation, which is also the argument behind asking for more predictable hours.
What an employer can and cannot ask
You do not owe a reason, and inventing one creates a second problem. The EEOC's guidance is narrow and useful: disability-related inquiries of an employee are allowed only when job-related and consistent with business necessity, and any medical information obtained — including information an employee volunteers — must be treated as a confidential medical record (EEOC). Those rules sit under the ADA, which the EEOC's fact sheet says covers private employers with 15 or more employees (EEOC).
Two practical consequences. If your limit really does rest on a medical matter, the channel is the leave or accommodation contact, not the group chat, and the difference between those channels is the subject of paid time off, sick leave and FMLA. If it does not, "a fixed personal commitment" is a complete sentence, and you can stop there.
Example: a Tuesday finish at 4 pm
Example. You need every Tuesday to end by 4 pm from the October roster, permanently. The message is one paragraph: "From the October roster, please record my Tuesday availability as ending at 4 pm. Every other day is unchanged. Is there a form I should complete, and when will the change show in the system?" No reason, one date, one time, one question about the record.
Now the arithmetic that decides whether to ask for the finish or the notice. If Tuesdays currently end at 6 pm and the October roster runs four Tuesdays, the fixed-finish request moves eight hours of scheduled work. At Washington's 2026 minimum wage of $17.13 an hour, that is $137.04 of hours you are asking to give up, so the request should say whether you want those hours back elsewhere in the week (Washington State Department of Labor & Industries). If you do, say so in the same sentence; a scheduler who reads "ends by 4 pm" alone will often just cut the shift.
Close the loop on the record
Ask two questions after any yes: who updates the scheduling system, and how you will see that it happened. An acknowledgment in chat is not a record. Check the next roster against the date and the time you wrote, and if it conflicts, point at those two values rather than retelling anything.
For a temporary limit, put the end date in your own calendar with the sentence you will send: "My 9 am start restriction ended on 23 October; my availability is back to the earlier pattern." That one line stops an old arrangement from following you into next spring's roster.