The simple past tense form of the verb buy is bought. Buy is an irregular verb, so it doesn’t add “-ed” to form the past tense.
Bought and brought are commonly confused words, but they can’t be used interchangeably. Brought is the past tense of the verb bring.
Liam went to the shop and brought a new hoodie.
Liam went to the shop and bought a new hoodie.
You can make sure you are using the correct past tense of buy with the QuillBot Grammar Checker.