Casting now and releasing later are separate moments
In D&D 2024, readying a spell casts it immediately and spends its casting resources; the energy waits for your reaction. When using a spell slot, do not wait to see whether the trigger occurs before subtracting it from your sheet. That cost matters before you end your turn.
DnD Dynamic Sheet can track actions, resources, notes and spells. This guide proposes manual record keeping. It does not claim that the app detects triggers or automatically spends resources for Ready.
A doorway nobody may cross
Suppose your character wants to ready a spell with a casting time of one action, using an available slot. You choose a perceivable trigger: a creature enters through the named doorway. Check the chosen spell, targets and requirements with the DM before assuming the response is legal.
On your turn, you take Ready and cast the spell, spending the slot. Holding its energy requires concentration, no later than the start of your next turn. If the trigger happens, you can use your reaction immediately after it finishes or ignore it. Broken concentration dissipates the spell without an effect.
These conditions come from Ready in the official 2024 Basic Rules glossary, consulted on 27 October 2026. They do not extend Ready to other casting times or turn a Bonus Action into a Reaction.
Update three parts without spending twice
Your own note might say, “Ready: north doorway; slot spent; energy held with concentration; reaction still available.” This is an invented example, not an included app card.
When preparing it:
- Mark the action used according to your table’s resolution.
- Reduce the resource actually spent. If represented by a custom counter, check its name and value before reducing it.
- Note the trigger and concentration, keeping the reaction available while it remains unused.
If the trigger happens and you release the spell, update the reaction. Do not subtract the same slot again as though you had cast a second spell. This distinction neither allows two reactions nor overrides other rules affecting the character.
If the trigger never happens
At the start of your next turn you can no longer hold that energy through this Ready. The resource was spent when casting; the creature failing to enter does not undo that moment. If a specific exception applies, review its text rather than returning a slot by habit.
Before choosing Ready again, compare its cost with acting immediately or taking another legal action. This article recommends no universally best spell and guarantees no successful hit on release.
DnD Dynamic Sheet is an available Windows x64 beta with initial online activation and local character data. Read its capabilities and counter example and presentation. Prepare your own note with a spell you know and confirm its cost before waiting for the trigger.