Here's a fun one to checkout:

Asteroid Lie # 26955

By sign and house may indicate what someone is more likely to lie about or how they lie, or get lied to or lie to themselves or who lies to them.

Aspects at tight orbs only, can be more telling (0-2° since this is an Asteroid with little to no energy and soft aspects must be exact).

Synastry with personal planets ....

I think all the planets can lie, especially when acting out their shadows.

Neptune to natal planets...harsh aspects yet have also seen it with conjunctions...trines (like Elsa mentions above) might make lying easy peasy (the trine is a line of least resistance kind of thing.) 

Neptune lies can be to save someone from hurt feelings, to try to fit an image we feel others want, to dream oneself up, to think oneself as perfect or ideal...

Pluto in aspect to personal planets for other reasons could lie...like persuading others to do x or y, or for power or to protect oneself...

Having these above aspects doesn't mean people lie yet I do think some lying is simply human.

I have neptune square sun and opposite the moon and trying not to delude myself in some life area is a life long feat. My husband often helps me see where I'm doing this.

I try not to lie yet I'm human so sometimes it happens. Since some bad decisions last year (sold a troubled car to a dealership to get rid of it badly) I'm cleaning up my integrity levels. I know that karma was collected or will be collected.

Sometimes I tell white little lies to get privacy from a nosey person yet try more and more to say instead that I'd rather not share/say...My friends know I'm very honest and I hold to that sometimes bluntly.

My father is a pathological liar due to toxic shame (under the age of 5 this shame develops) and narcissism. Luckily he's now a benign narcissist (I've always said Hitler would have mellowed in his 70s.) I accept him now as he is (took decades) as he's unwell, clearly. It's bloody foggy, the sensation that comes from his constant lying, so I feel the same when others lie big time in my presence.

I'm trying to think if I lied today...No, I didn't, yey!! A win.

And I'm pretty sure I've never lied here at EE, ah! (Just scanned mentally my writing here.)

Was I lied at today? It's probable in my line of work! No problem. I think I'm good at picking up big lies (8th house planets) which are the ones I care about more.

Gosh, am I becoming more accepting or what? Maybe.

Just to finish this long post. Like 10 years or so ago I read the book 'The Four Agreements' by Don Miguel Ruiz. Such a great book! It mentions not lying  as an agreement with oneself amongst other things.

I try to follow its principles yet fail at times...Human (eyes rolling.) It's okay, I tell myself when this happens, and then I tell myself I'll try again the following day. I'm a pisces so I feel guilty for lying, especially if I'm aware of it.

Planets in Gemini (could just make for a master storyteller or town gossip!)

A classic quote by Dr. House (played by a Gemini actor):

EVERYBODY LIES.

Don't know how I forgot this post!

To me Mars in Libra is more likely to just not say anything. So it's not going to lie it's just 'yeah I'm not going to talk about that' or just *silence*.

But we're all going with Neptune Mercury?

I occasionally tell a kind of lie that feels like it is divinely inspired. It's bizarre. I recall telling someone of a dream and implying things are going to be OK even though I knew what I was saying and how I was translating it was not at all true. It comes from an extreme anger. Like I want to lie because I know the lie will harm the person but it's also what they want to hear. It happens in a more general sense quite a bit and I say things that I am not consciously aware of are not true but they are definitely not true. Sometimes I get guilty though and say 'I don't what to lie to you this is what I mean'.

I’m a pisces so I feel guilty for lying, especially if I’m aware of it.

I would imagine someone who is capable of standing up for themselves and saying what they mean are the least likely to lie. Also those who find a way to avoid intepersonal emotional complexity... Somehow! And those who are economically independent!

Lying is different from 'withholding'. I think the madness and mental process of Gemini would actually go as far as to justify the lying. But it would be stronger in certain aspects.

Elsa said
A trine between Mercury and Neptune might be even worse.

  

Can I ask why you think so, Elsa? It's very interesting...

I've found that Mercury at 29 degrees can have a compulsive communication style. Mixed with the right aspects, it can be compulsive lying.