When negating a BA structure, the negators méi(yǒu) ‘did not’, ‘have not’ (used in statements) and bié or bù yào ‘do not’ (used in imperatives) are always placed before BA in the sentence:
tā méi yǒu bǎ mào zǐ dài shàng 。
He didn’t put his hat on.
bié bǎ wǒ de dōng xī gǎo luàn le 。
Don’t mess up my things.
The BA structure in a statement or question usually expresses an action which has already been realized, and the negator (as above) is likely to be méi(yǒu). However, bù may be used with it, where a condition is stated:
mǔ qīn duì hái zǐ shuō ：nǐ bú bǎ jiá kè chuān shàng ，bié chū qù wán 。
Mother said to her child: ‘If you don’t put on your jacket, you mustn’t (lit. don’t) go out and play.’
 Yip, P. C., Rimmington, D., Xiaoming, Z., & Henson, R. (2009). Basic Chinese: a grammar and workbook. Taylor & Francis.