Daily Halacha - Laws of Rosh Hashanah, 2nd of Tishrei 5778

Until when is one permitted to cook from Yom Tov for Shabbat?

Ideally, one should complete all cooking from Yom Tov for Shabbat by the afternoon hours and not delay until close to Shabbat. However, if one is delayed, they may cook until close to sunset [Chazon Ovadia Yom Tov, p. 278].

If someone cooked without an Eruv Tavshilin, is the food forbidden?

One who transgressed and cooked from Yom Tov for Shabbat without preparing an Eruv at all may, after the fact, eat the food that was cooked, even if they have other foods to eat [Chazon Ovadia, p. 292].

Ach Tov VaChesed - Daily Halacha