parent of a 21 year old with Asperges and ADHD

Tony Attwood's Complete Guide to Asperger's Syndrome has a very brief reference to lying under Theory of Mind (ToM), but on looking at it, it might make sense of your son's situation.

It may be "to deceive people and avoid anticipated consequences". I surmise that, if you live a life where you are often in the wrong, by virtue of the disability, it comes easier to avoid the negative impacts by lying, however absurd this tactic might seem.

"due to impaired or delayed ToM abilities, the person with Asperger's syndrome may not realize that the other person is likely to be more offended by the lie than by any apparent misdemeanour."  This might sound strange, but people on the spectrum really don't get much feedback of people's reactions and it may be as a consequence of that that he may really not realise how bad his lying sounds to you. Again you have to consider how many negative blows to self-esteem a person with Asperger's gets in a day - it is amazing how most survive at all. 

"lying can aso be a way of maintaining self-esteem", especially if he comes to feel that avoiding mistakes at all cost is preferable.

It might be better to try to find out why, other than the above reasons, he prefers lying. Can you ascertain the damage to self esteem that he experiences? What is happening to him, not necessarily things you'd know about, in his relations with others including peers and other people's reactions? Any bullying/public ridicule/people taking advantage still going on?

Money matters have been discussed on here a lot, so worth searching the community, the search box on the left. Again profligacy might be a counter to low self-esteem.

Time on the computer is an escape from harsh reality. 

Tony Attwood's Complete Guide to Asperger's Syndrome has a very brief reference to lying under Theory of Mind (ToM), but on looking at it, it might make sense of your son's situation.

It may be "to deceive people and avoid anticipated consequences". I surmise that, if you live a life where you are often in the wrong, by virtue of the disability, it comes easier to avoid the negative impacts by lying, however absurd this tactic might seem.

"due to impaired or delayed ToM abilities, the person with Asperger's syndrome may not realize that the other person is likely to be more offended by the lie than by any apparent misdemeanour."  This might sound strange, but people on the spectrum really don't get much feedback of people's reactions and it may be as a consequence of that that he may really not realise how bad his lying sounds to you. Again you have to consider how many negative blows to self-esteem a person with Asperger's gets in a day - it is amazing how most survive at all. 

"lying can aso be a way of maintaining self-esteem", especially if he comes to feel that avoiding mistakes at all cost is preferable.

It might be better to try to find out why, other than the above reasons, he prefers lying. Can you ascertain the damage to self esteem that he experiences? What is happening to him, not necessarily things you'd know about, in his relations with others including peers and other people's reactions? Any bullying/public ridicule/people taking advantage still going on?

Money matters have been discussed on here a lot, so worth searching the community, the search box on the left. Again profligacy might be a counter to low self-esteem.

Time on the computer is an escape from harsh reality.