“I'd like to resign, effective next month.”
Effective followed by a date means beginning or taking effect then. It is used formally for resignations, transfers, and new rules. Frank asks to resign starting next month.
B1-41 / CEFR B1 / EPISODE 41
Explaining a resignation and handover
SceneFrank is in his boss's office with a folder of notes.

WORDS & CONTEXT
Effective followed by a date means beginning or taking effect then. It is used formally for resignations, transfers, and new rules. Frank asks to resign starting next month.
In American English, a raise is an increase in pay; British English commonly uses rise. Common phrases include get a raise and ask for a raise. The manager offers higher pay to persuade Frank to stay.
Transition notes are documents passed to a successor when someone leaves or changes jobs. Transition means a change from one situation to another. British English often uses handover notes.