1, notice must pay attention to retaining evidence, in written form, please sign for it, and pay attention to keeping a copy.
If the company doesn't sign for it, it will send another copy to the company by EMS express mail, with the envelope marked with "resignation letter" and its real signature, and ask the post office to return the receipt signed by the company or its copy.
If the company refuses to sign for the express mail, it can also use the "refusal" receipt or letter rejection certificate written by the postman as evidence of the notice.
There is also a resignation letter that goes directly to the labor department and asks for help. The labor department will notify the unit to sign it! The evidence retained in this way is the best!
The normal resignation procedure is generally stipulated in the clause of one month in advance. Even if you can prove that you handed in your resignation letter the day before, the company can handle it the day after tomorrow, which makes no sense. The key is whether the company will settle your salary and benefits after you go through the formalities. Generally, private bosses' companies are particularly picky and rarely meet generous ones. Alas, the work is so hard. .