Grammar fix
follow through on a promise
carry out a promise
To do the thing you promised to do.
How oftenCommon
LevelB2
Used inSpeech & writing
Hear it in context
Notice where the phrase sounds natural.
She promised to send the documents by Friday and followed through on it.
My friend said she would help me move house, and she followed through on her promise even though she was busy that weekend.
Fix the pattern
One small grammar move makes it sound right.
Not: follow through a promise
Say: follow through on a promise
Use the preposition 'on' after 'follow through'.
Don't confuse it
Other ways to say it
Do what you said you would
How formalConversationalMore formal
keep your wordDo what you said you would do.
follow through on a promiseYou're here · Carry out the action you committed to.
honour a promiseMore formal: fulfil a commitment you made.