How do spell slots and preparation work when multi-classing between cleric and bard

Question

I'm planning to play a multi-class bard/cleric character, and I wanted to verify how spell preparation and slots work across the two classes, particularly since they use different approaches for casting.

• Can spell slots from the the total number available from the Multiclass Caster table (PHB pg165) be used to cast either known Bard spells or prepared Cleric spells?
• Is it correct that Cleric spells must still be prepared each day from the set of available Cleric spells for the character's level?
• Is it correct that Cleric spells must use Wis as the primary stat, and Bard spells must use Chr?

I'm sorry if this has already been asked before, I couldn't find an answer on first look. Thanks.

Answer 1

The multiclassing rules in Chapter 6 of the PHB cover this.

Can spell slots from the the total number available from the Multiclass Caster table (PHB pg165) be used to cast either known Bard spells or prepared Cleric spells?

Yes. A Bard 4 / Cleric 4 can cast four first level spells and three second level spells per day (and a few higher level spells). These could be all cleric spells, all bard spells, or a mix between the two. You make the choice as you cast the spells (as always).

Note that multiclass characters will often have spell slots whose level is higher than any spell that character can prepare. You can use these slots by casting spells at a higher level. For example, our Bard 4 / Cleric 4 could cast Cure Wounds as a 4th level spell, but couldn't prepare Banishment.

Is it correct that Cleric spells must still be prepared each day from the set of available Cleric spells for the character's level?

Yes. Page 164 (under the Spells Known and Prepared heading) spells this out pretty clearly:

You determine what spells you know and can prepare for each class individually, as if you were a single-classed member of that class.

Is it correct that Cleric spells must use Wis as the primary stat, and Bard spells must use Chr?

Yes. Again, page 164 spells it out:

Each spell you know and prepare is associated with one of your classes, and you use the spellcasting ability of that class when you cast the spell.

Answer 2

Yes to all.

• The spells slots you have available to use are those on the Multiclass Caster table, and you can use them for any known and prepared spells of appropriate level.
• Cleric spells must be prepared each day and can only be prepared according to your Cleric level. Likewise, Bard spells known are according to your Bard level.
  
  You may have higher spell slots than your ability to learn spells. For example, when reaching Cleric 1 / Bard 6 you gain 4th level spell slots, but you cannot learn nor prepare fourth level spells.
  
  Nor can you use a Lore Bard's Additional Magical Secrets to gain a 4th level spell as you have only 3rd level Bard spell learning abilities. You can, however, cast lower level spells like Dissonant Whispers or magically secreted Fireball using that 4th level spell slot for extra damage.
• Your Cleric spells will use Wis and Bard spells Cha.

Answer 3

As someone who builds multiclass almost any time it is allowed, I have been over this a lot and, unfortunately for us multiclassers, this is a case of a rule trumping/replacing another rule, not combining rules. The confusion arises from this important distiction being forgotten because it's easy to misread what is trumped and what is combined, which I'll get into presently.

The 'Classes' section and coresponding write ups of each class assume you are Single Classing. If you are multiclassing, some rules are different for you. The section on Multi Classing details How the rules for you are different than single class characters for spellcasters, this includes how you determine what spells you know and prepare and what spell slots are available to you. Instead of the rules in the 'classes' section, you use the rules in the 'Multi classing' section just like you do for skill and saving throw proficiency. The problem arises because the multiclass rules for spells known ask you to reference the 'classes' section but with an important caveat. It does look, at first glance, like you could prepare/learn spells of your highest multi class slot level, using the rules from 'Classes' but the multi class section, before directing you there, states you determine spells known/prepared based on your individual levels in a given class.

So, a wizard 3/Cleric 10, when referencing the wizard rules to determine what sweet wizard spells they have access to, must remember they can learn/prepare only those spells available to 3rd level wizards even if they have 10 levels of cleric as well. The spellbook and spells at higher level blurbs do state that they can learn/prepare any spell for which they have slots available (in this case 7th), but the multi class rules, which trump single class rules in this instance, state they calculate what wizard spells they can Learn/Prepare as if they were a 3rd level wizard only (in this case 2nd level spells max) and their cleric spell access as if they were a 10th level cleric only (in this case 5th level spells max).

Their spell slots available are the only time they combine caster levels, which is why the rule looks fuzzy because if i have 6th level spell slots, why can't I prepare disintegrate? because you determine wizard spells known/prepared as a 3rd level wizard, who would not have 6th level slots. They need to post an errata or something to make this clearer, that's all I mention all this because the 2nd question has been a subject of debate a lot.

Taking this into account

Question 1) Yes 100%. Total spell slots available for whatever spells you know are determined by combining spellcasting levels, what spells you have access to are determined individually.

2) Yes but spells available are determined by Cleric level and what slots a cleric of that level would have, not the max slots you as a multiclass cleric/bard have. Same goes for what bard spells you know.

3) Yes each spell you know and prepare is associated with one of your classes (Bard or Cleric for you), and you use the spellcasting ability of that class when you cast the spell. Similarly, a spellcasting focus, such as a holy symbol, can be used only for the spells from the class associated with that focus.