labour charges

Mr. A ( civil contractor, registered under GST ) provide labour services to Mr. B (civil contractor, registered under GST ).

Mr. B every month deposited sum amount after deducting
TDS in Mr. A's bank account. Mr. B has paid GST @ 18% Under RCM.

Mr. A does not provide any invoice regarding this amount and labour charge setvice.

is mr. A is liable to pay any GST ?