When you join a company you are supposed to bring your documents and some insist on you bringing your log book. If you have fake docs, then the truth is harder to find. Although, the licensing authority should query something like an A320 endorsement going on a PPL.
I know of one person who's job offer was retracted after it was found he lied about his experience.
He had claimed to have flown for a particular company in the Kimberley, Australia. The prospective company had just employed the old company's chief pilot. He was asked about Bloggs, the reply was "never heard of him". When the liar was asked about the specifics, he 'fessed up to lying and he lost the job. No idea if any punitive measures were taken. He had the qualifications, just not the experience.
Most of the time, "Walter Mittys" are found during simulator checks and fired.