Safek Brachot LeHaKel
If one's in doubt if one made a bracha
- If one is in doubt whether one can make a Bracha the general rule is that one shouldn’t make the Bracha. 
- If one is in doubt whether one made a Bracha Rishona or not, one may not make the Bracha, rather it’s permissible to eat without a Bracha because of Safek Brachot LeHakel. 
- If there’s a doubt whether one interrupted his eating (with a Hesech Hadaat) one shouldn’t make another Bracha and it’s permissible to continue eating. 
- If a person has two factors to make a bracha (Safek Safeka) he still shouldn't make the bracha.
Alternatives to saying the actual bracha
- It’s preferable to make the same Bracha on another food upon which one didn’t originally intend to eat and have intent to cover the doubt one is in. 
- Alternatively it’s preferable to listen to someone making that Bracha, while the one making the Bracha has intent to fulfill the obligation of the one listening and the one listening should intend to fulfill the obligation. 
- Another preferable option is to obligate oneself to make another Bracha by making a proper Shinui Makom. 
- In these situations there are a number of suggestions of how to make the Bracha without making an unnecessary Bracha.
- Some say that one can say the Bracha in a language other than Hebrew or in Hebrew with another nickname of Hashem, however, many great authorities disagree and forbid this. 
- Some say that one may say the Bracha as part of learning (reading it from Shulchan Aruch or Rambam), however, many argue that this too is forbidden. 
- Some say that one should think of the Bracha or at the name of Hashem and not verbalize it. 
- Some say to read the פסוק of Vayivarech David until the words MeOlam VeAd Olam and then conclude the Bracha according to the appropriate ending. 
- A minority opinion holds that you can recite the bracha in a manner of praising Hashem without intent to fulfill the bracha.
- One should be very careful not to say a Bracha Levatala, a Bracha in vain, or cause oneself to make a Bracha Sheina Tzaricha, an unnecessary Bracha. If one said a Bracha Levatala or say Hashem's name in vain, one should say "Baruch Shem Kavod Malchuto LeOlam VaEd". 
- If after saying Baruch Atta Hashem one realizes that one shouldn't say that Bracha, one should conclude with the words "Lamdeni Chukecha", which is a pasuk in Tehillim and the Bracha isn't Levatala.
- If one already said Elokey and didn't say the last syllable, Nu, then one should conclude with the words "Yisrael Avinu MeOlam VeAd Olam", however, in this case one should also say Baruch Shem afterwards.
- If one recited a Bracha Rishona while holding a specific food and it fell on the floor (rendering it inedible) before one has the chance to take a bit from it, it depends on the situation as to whether one's original bracha was invalid and a new bracha is necessary if one wants to eat food of the same kind.
- If one intended not to include any other food with that Bracha, one's original bracha is a Bracha Levatala. In such a case, one should recite Baruch Shem Kavod Malchuto LeOlam VaEd. 
- If one intended to include other food in one's bracha, then even if that food is somewhere else, one's original bracha is valid.
- If one didn't specifically mean to include or exclude other food that was in front of him from his bracha, one's original bracha is valid.
- If one had a bread meal, was full, and is in doubt whether one made Birkat Hamazon, one should say Birkat HaMazon since Birkat HaMazon is Deoritta.  However, if one’s not full or isn’t sure if one’s full, one doesn’t make Birkat HaMazon. 
- If one had a Kezayit of mezonot and is in doubt whether one made Al HaMichya, one should and may not go ahead make Al HaMichya out of doubt rather one should be careful to eat another Kezayit (without a Bracha Rishona) and then make Al HaMichya.  See Bracha Achat Mein Shalosh#Al Hamichya for details.
- After the fact if one recited mezonot on anything besides water or salt one fulfilled one's obligation.
- After the fact if one recited shehakol on anything one fulfilled one's obligation.
- After the fact if one recited Birkat Hamazon on wine or dates one fulfills one's obligation.
- After the fact if one recited Birkat Hamazon on mezonot, even though there is a dispute whether one fulfilled one's obligation one should not recite a new bracha since according to many poskim one fulfilled one's obligation.
- After the fact if one recited Birkat Hamazon on shivat haminim one doesn't fulfill one's obligation.
- After the fact if one recited Al Hamichya for Birkat Hamazon one fulfills one's obligation.
- After the fact if one recited Al Hamichya for Boreh Nefashot one doesn't fulfill one's obligation.
- Rif Brachot 12a, Shulchan Aruch 209:3, Kitzur Shulchan Aruch 6:6; Kitzur Shulchan Aruch of Rav Mordechai Eliyahu 6:6
- Shulchan Aruch in 167:9 and 209:3 writes clearly that if one is in doubt whether one made a Bracha one doesn’t not go back and say it except for Birkat HaMazon. Mishna Brurah 167:49 adds that it’s forbidden to make a Bracha in a case whether there’s a doubt.
- VeZot HaBracha (beginning of chapter 10, pg 87)
- Mishna Brurah 215:20 quotes the Chaye Adam who says that for a Safek Safeka you can't make a bracha in a case of safek safeka. However, in Mishna Brurah 4:30 he quotes Rabbi Akiva Eiger (Magen Avraham 4:12) who says you can make a bracha because of a safek safeka.
- Vezot HaBracha (pg 87, chapter 10)
- Mishna Brurah 167:49, Vezot HaBracha (pg 87, chapter 10)
- Vezot HaBracha (beginning of chapter 10, pg 87) in name of Rav Elyashiv
- Rabbi Akiva Eiger 1:25 writes that it is forbidden to say a bracha with a nickname of Hashem because it is considered saying a name of Hashem in vain. Even though the Shach says you can erase a nickname of Hashem that's only erasing it but mentioning it is still forbidden. Therefore, unless one is obligated one may not say the bracha with a nickname of Hashem. However, Aruch Hashulchan 202:3 argues that you can say the bracha with a nickname of Hashem and it isn't an issue of saying Hashem's name in vain since it is only a nickname. Mishna Brurah 215:11, Piskei Teshuvot 209:7, Pri Megadim (M”Z 219:3), Sh”t Igrot Moshe 4:40:27, 4:49, and Chazon Ovadyah Sukkot (pg 245) agree with Rabbi Akiva Eiger and in cases of doubt forbid saying Bracha with the language of Barich Rachmana Malka DeAlma and continuing with the text of the bracha.
- Piskei Teshuvot 209:7
- Piskei Teshuvot 209:7, Kaf HaChaim 157:10, Vezot HaBracha (beginning of chapter 10, pg 87)
- Halichot Shlomo (Tefillah 22:22) writes that one should recite the pasuk if Vayivarech Dovid... Baruch Atta Hashem Elokey Yisrael Avinu Molam Vad Olam and then continue with your bracha. He says that you can use that if you're unsure if you said a bracha but not if the halacha is that you don't recite a bracha because of a doubt. He says that saying it for no reason is a degradation of Hashem but saying it for a bracha starting with a pasuk isn't inappropriate.
- Chashukei Chemed Niddah 73a relies on the Chavot Daat (Bet Hasafek 110:20) who holds that one can recite a bracha one isn't obligated in as a praise to Hashem as long as one doesn't intend for it to be a bracha.
- Rabbi Tanchum in Yerushalmi Brachot 6:1 explains that if one made a bracha levatala he should say baruch shem kavod malchuto lolam vaed. Tosfot Brachot 39a s.v. basar, Rabbenu Yonah Brachot 28a s.v. ubyerushalmi, Rosh 6:20, Rambam Brachot 4:10, Rambam Shevuot 12:11, Shulchan Aruch OC 206:6, and Kitzur Shulchan Aruch 6:4 codify this Yerushalmi. Rambam Shevuot explains that it is effective so that the mentioning of Hashem's name shouldn't be in vain but that it should be mentioned for a praise. Chazon Ish OC 137 thinks that this reason can only if bracha levatala is derabbanan and not deoritta. Aruch Hashulchan 206:16 implies that baruch shem is a fix for bracha levatala completely.
- Rabbenu Yonah Brachot 28a ubyerushalmi, Kitzur Shulchan Aruch 6:4, Aruch Hashulchan 206:16
- Kitzur Shulchan Aruch 6:4
- Shulchan Aruch and Rama 206:6
- Rama 206:6, Mishna Brurah 206:26. See Yeshuot Dovid ch. 2 who quotes the Halacha Brurah Minchat Shmuel who says fundamentally Shulchan Aruch agrees with the Rama when a person has direct intent to exempt other food. See there for his proof from Shulchan Aruch 206:2.
- Mishna Brurah 206:26 writes that if one didn't specifically intend to include or exclude any food one had in front of him, then if the food which one's holding falls, one should not recite a new bracha because of Safek Brachot LeHakel.
- S”A 209:3
- Mishna Brurah 209:10 writes that one makes Birkat HaMazon out of doubt only if one’s full. Kaf HaChaim 184:20 (quoted by VeZot HaBracha (pg 87, beginning of chapter 10) adds that even if one is in doubt whether one’s full, one doesn’t make Birkat HaMazon.
- Mishna Brurah 209:10
- Chaye Adam (v. 1, 58:3), Halacha Brurah 206:7, Igrot Moshe OC 4:40. Ritva Brachot 2:16 writes that after the fact Mezonot is effective even for bread.
- Chaye Adam (v. 1, 58:5)
- Rabbenu Yonah (Brachot 6a s.v. iy nami) proves from Brachot 12a that birkat hamazon exempts dates and from Brachot 35b that it covers wine. He reiterates the point in Brachot 29b s.v. miyhu. Rosh (Brachot 1:14 and Pesachim 10:10) and Rashba (Brachot 42a s.v. yayain) agree. (See Pri Chadash 208:17 who writes that the Rashba only meant that wine is exempt when it is part of the meal.) Rashba (Brachot 41b s.v. heviyu) shows that the Yerushalmi and Bahag hold that birkat hamazon doesn't exempt dates. Shuchan Aruch OC 208:17 rules like the Rabbenu Yonah, Rosh, and Rashba.
- Based on 41b, both the Rabbenu Yonah (Brachot 29b s.v. lacher) and Rashba (Brachot 48a s.v. ha, 41b s.v. meha, 42a s.v. yayin) write that birkat hamazon doesn't exempt mein shalosh even after the fact. Shulchan Aruch OC 208:17 codifies their opinion. Bear Hagolah and Pri Chadash 208:17 argue with Shulchan Aruch for all mezonot foods since they are filling. Rabbi Akiva Eiger 208:17 comments that for pat haba bkisnin certainly birkat hamazon does exempt it. Mishna Brurah 208:75 concludes that since many achronim disagree with the Shulchan Aruch and hold that birkat hamazon exempts any mezonot since they are more filling than dates which the birkat hamazon covers. He adds that certainly we accept Rabbi Akiva Eiger regarding pat haba bkisnin. Birkat Hashem 2:3:22 agrees.
- Even though the Rashbam Pesachim 103b writes that if mein shalosh is effective on a food then certainly birkat hamazon is effective. This is also found in the Baal Hameor Pesachim 24b but Ramban rejects it. Additionally, Tosfot Pesachim 103a rejects this types of kal vchomer. Tosfot Rabbenu Yehuda Brachot 41b s.v. maskana, Rashba 42a s.v. yayin, and Rosh Pesachim 10:10 agree with the Tosfot against the Rashbam. Shulchan Aruch OC 208:17 follows the Tosfot unlike the Rashbam. The Mishna Brurah 208:75 accept this ruling of Shulchan Aruch. Aruch Hashulchan 208:27 explains that the reason it doesn't work is because only the original bracha that chazal instituted for that food works and nothing else. The only exceptions are when the bracha would have been relevant even according to chazal but practically didn't establish it for some reason (such as for wine and dates).
- Raah (Brachot 44a) explains that since Al Hamichya is Biblical and the pasuk which indicates the obligation for Birkat Hamazon includes the obligation for Al Hamichya if one says Al Hamichya in place of Birkat Hamazon after the fact one fulfills one's obligation. This is also the opinion of the Bet Yosef 168:6 who rules that for all forms of pat haba bkisnin one should recite Al Hamichya even though potentially it could be bread. Gןinat Veradim 1:24, Birkei Yosef 167:10, and Birkat Hashem 2:3:18 agree. The Ginat Veradim explains that this idea is based on the Kesef Mishna Brachot 2:1 who quotes the Rambam and Ramban that Birkat Hamazon is deoritta but the number of brachot are derabbanan.
- Shulchan Aruch OC 208:13