Shabbos and Yom Tov:
Shabbos and Yom Tov are not a time for Tefillin and one is thus not required to wear Tefillin on Shabbos or Yom Tov. Furthermore, it is even forbidden to wear Tefillin one these days for the sake of the Mitzvah. One who dons Tefillin on Shabbos or Yom Tov for the sake of the Mitzvah transgresses the Biblical prohibition of â€œBaal Tosef/Do not addâ€ and in addition is belittling the sign of Shabbos and Yom Tov and is thus liable for death. It is however permitted to wear Tefillin not for the sake of the Mitzvah but for some other purpose, such as one who found lost Tefillin in an area without an Eruv and desires to wear it until he reaches a secure area.
It is forbidden to wear Tefillin on Shabbos and Yom Tov for the sake of the Mitzvah.
If after accepting Shabbos early one remembered he did not put on Tefillin, may he still do so?
If one accepted Shabbos early, prior to sunset, it is permitted for him to wear Tefillin without a blessing up until sunset, if he has not yet done so that day. This applies even if he already Davened Maariv. It is best however for him to do so with a Tnaiy, as stated next.
If sunset has already arrived on Erev Shabbos, may one still put on Tefillin if he has not done so that day?
No. However, from the letter of the law one may wear the Tefillin without a blessing and with a Tnaiy that if its already Shabbos then he is intending not to fulfill the Mitzvah with the Tefillin.
Are Tefillin Muktzah on Shabbos?
Tefillin are considered a Keli Shemilachto Leissur. Thus, they may be moved in order to use them for a permitted purpose or if one needs to use their space, however they may not be moved for their own benefit, such as to save them from getting stolen. However it is permitted to move them in order to prevent desecration of the Tefillin.
May one lift Tefillin from the ground on Shabbos?
Yes. Tefillin which have fallen on the ground may, and thus must, be lifted in order to prevent their belittlement.
May one move his Tefillin out from the rain or from the sun?
If one fears that they may otherwise get ruined, and he is not able to cover them with a vessel, then he may move them, as having the Tefillin get ruined is a disgrace to the Tefillin.
May one remove Tefillin from his bedroom in order to permit marital relations?
Some Poskim rule it is permitted to do so. However, from other Poskim it is implied it is forbidden to do so. According to the latter opinion one is to either remove the Tefillin with an irregularity or cover the Tefillin with a double covering.
 The reason: The purpose of wearing Tefillin is to serve as a sign between us and Hashem. This is learned from the verse [Shemos 13/9] â€œAnd it shall be for you a signâ€, [which teaches that Tefillin are donned only when they alone are a sign and not when something else is also a sign]. Now, Shabbos and Yom Tov is itself a sign between Hashem and the Jewish people as the verse [Shemos 31/13] states â€œAs it is a sign between me an youâ€, and hence one is not required to wear Tefillin on Shabbos and Yom Tov. Furthermore it is even forbidden to do so due to Baal Tosif and it belittling the sign of Shabbos. [Admur ibid; Rebbe Akiva in Eruvin 96a and Menachos 36b; see there for the other source suggested]
 Admur ibid; Michaber ibid [is belittling]; Mâ€A 31/1 and Rashba 1/61 and Eiruvin ibid [is Baal Tosif]
The reason: As by fulfilling a different sign between Hashem and the Jewish people on Shabbos and Yom Tov he belittles the sign provided by Shabbos and Yom Tov. [Admur ibid; Michaber ibid]
 Admur ibid; Mâ€A 29
 This follows the final ruling of Admur in 30/5 who suspects for the second opinion there regarding wearing Tefillin on a weekday after Maariv. [See Halacha?] and the same would apply regarding Maariv of Erev Shabbos as rule regarding Shofar of after Maariv on Erev Shabbos: Taz 600/2; Erech Hashulchan 600/2; Elya Raba 601; Ikarei Daat 30/24; Mâ€E 601/13; Chayeh Adam 144/20; Mâ€B 600/7; See Os Chaim Veshalom 30/4; Beir Moshe 1/15 and Poskim listed there who all imply that we rule like the Taz ibid even on Erev Shabbos regarding Tefillin, and they remain with a Tzaruch Iyun Gadol as for why the Taz ibid does not bring this down here.
Other Opinions: According to the first opinion in Admur ibid it is forbidden to wear Tefillin after Maariv even during the weekday and certainly on Erev Shabbos. So also rule some Poskim regarding Shofar on Erev Shabbos that it cannot be blown even without a blessing. [Mor Uketzia 600; Hagahos Hatur brought in Kaf Hachaim 600/12]; However some Poskim rule that he may blow the Shofar even with a blessing. [Michtam Ledavid 17; Birkeiy Yosef 600/5, brought in Kaf Hachaim 600/11]
Ruling of Piskeiy Teshuvos: Piskeiy Teshuvos 31/1 rules as follows: If one has accepted Shabbos but has not yet Davened Kabalas Shabbos [this means that he has only accepted upon himself Tosefes Shabbos, such as through verbally or mentally stating that he is accepting Shabbos], then if it is prior to sunset, he may put onTefillin. This applies by both Tefillin of Rashi and Rabbeinu Tam, and a blessing may be recited on the Rashi Tefillin. If however he already Davened Kabalas Shabbos/Maariv, then he may no longer wear the Tefillin. [Piskeiy Teshuvos ibid footnote 3 that this applies even according to the lenient opinion in Admur 30/5 as here there is a prohibition according to all to put on Tefillin on Shabbos; Vetzaruch Iyun Gadol as the Taz ibid rules that one may blow Shofar even after Maariv, and that the Kabala is not considered a kabala, hence what difference would it make if he Davened Maariv or accepted Shabbos verbally!]
 Taz ibid regarding Shofar and the same reasoning would apply regaridng Tefillin
The reason: As one does not intend to accept Shabbos to the point that he canâ€™t fulfill a positive command. However a blessing may not be said as this shows that he is doing so for the sake of the Mitzvah and causes a contradiction. [Taz ibid; See Sefer Hachaim; Yalkut Gershoni 30; Mahrsham 3/333; Divrei Yisrael 165]
 The reason: To suspect for those opinions who hold it is already considered Shabbos for him and thus forbidden [Biblically!] for him to wear Tefillin.
 So rule regarding Shofar: Mateh Efraim 601/13; Mâ€B 600/7; Kaf Hachaim 600/13; Implication of Taz 600/2 [He differentiates between accepting Shabbos before Bein Hashmashos and Bein Hashmashos itself, saying that Bein Hashmashos is more severe. Likewise in the Teshuvah he always mentioned that the allowance is before sunset. However see Admur 261/3 that accepting Shabbos is more severe than Bein Hashmashos regarding doing Rabbinical Melacha.] See Piskeiy Teshuvos 31/1 footnote 1 that implies one may wear the Tefillin during Bein Hashamshos even without a Tnaiy. Vetzaruch Iyun Gadol, as perhaps it is already Shabbos and one cannot wear Tefillin on Shabbos
Other opinions regarding Shofar and Megillah: Some Poskim rule it is permitted to blow Shofar and hear Megillah on Bein Hashmashos of Erev Shabbos: Michtam Ledavid 17 [â€œcertainly he is to blowâ€]; and so rule the following Poskim regarding reading the Megillah: Pâ€M 692 Mâ€Z 3; Tzitz Hakodesh 55; Nitei Gavriel 31/10 footnote 15
The reason: As Bein Hashamshos is possibly already Shabbos, and it is forbidden to wear Tefillin on Shabbos. It is thus much more severe then simply one who already davened Maariv during the week. [See Piskeiy Teshuvos 31/1 footnote 3]
 See Admur 31/2; Piskeiy Teshuvos 31/1 footnote 3; See Piskeiy Teshuvos 31/1 footnote 1 that implies one may wear the Tefillin during Bein Hashamshos even without a Tnaiy. Vetzaruch Iyun Gadol, as perhaps it is already Shabbos and one cannot wear Tefillin on Shabbos
 308/19; See Rama 308/3; Mâ€A 308/11; Taz 308/3; Mâ€B 308/24; SSHâ€K 20/14
The Rama 308/4 rules that Tefillin are considered designated for a permitted use and may be moved for any need on Shabbos. This follows the ruling of Tosafus Beitza 15a â€œHachi Keamarâ€ that one may wera Tefillin on Shabbos, even though he is not obligated. [Mâ€A ibid] The Taz ibid and Magen Avraham ibid question this ruling, as in truth we rule in 31/1 like the Zohar that it is forbidden to wear Tefillin on Shabbos, and hence Tefuillin are considered MMâ€I. Admur rules like their opinion, although states that one may move the Tefillin in order to prevent its belittlement.
Other opinions-lenient-Milachto Liheter: Some Poskim rule that Tefillin are considered designated for a permitted use and may be moved for any need on Shabbos. [Rama 308/4] The Mâ€B 308/24 rules that one may be lenient in a time of need like this opinion. [Mâ€B ibid; Biur Halacha 31/1 â€œAssurâ€]
Other opinions-stringent-Chisaron Kis: Some Poskim rule that today Tefillin have a status of MMCâ€K being that today we are particular to not do any other use with the Tefillin other than its Mitzvah. [Bris Olam 11; Poskim in Piskeiy Teshuvos 308 footnote 195] SSHâ€K 20/14 rules that it is MMâ€I and not MMâ€CK, and in footnote 32 brings Rav SZâ€A who explains the reason for this is due to the fact that Tefillin is useable to guard one from Mazikim even on Shabbos. The Tosefes Shabbos 308/21 addresses this question, asking that according to the Mâ€A and Taz ibid that argue and rule Tefillin are considered MMâ€I then in truth it should be considered MMCâ€K, being that they are expensive and one is certainly particular not to use them for other matters. He explains that Sifrei Kodesh have a lesser status of Muktzah than do other items, as is seen from the law that they may be moved even for no purpose at all, as opposed to other items which are Melachto Liheter. Thus Tefillin are alos lowered from their true status of MMCK, to the status of MMâ€I.
 The reason: Since Tefillin are designated to be used specifically for their mitzvah, which is forbidden to be done on Shabbos, therefore they are considered a vessel designated for a forbidden use [Milachto L’issur]. [Admur ibid, based on Mâ€A ibid]
 Mâ€B 31/2; Biur Halacha 31/1 â€œAssurâ€ in name of Chayeh Adam
 Ketzos Hashulchan 108/18
 Harav Shlomo Zalman Aurbach in SSH”K 20/10 footnote 24
 The reason: As moving Tefillin from ones bedroom in order to permit marital relations is considered like limkomo and is permitted. [ibid]
 Tehila Ledavid 3/51; Beir Moshe 8/30-31
 This is dependent on whether moving the Tefillin in such a case is defined as moving for its space or not, as discussed in the above Poskim.