I've posted 2 embarrassingly long posts on pretty much the same topic, so I hope that this will be much shorter and a little different 
How would you/do you react if you find out your DH/DP has lied to you? Obviously cheating would be an instant LTB, but how would you react to smaller lies? For eg, telling you they were working but they were actually at the pub, lying about who they're meeting, concealing financial things, lying by omission etc.. Different reaction if it was just once or repeated many times?
Would it be an instant end to the trust/relationship or would you try and look into the reasons why they lied? Would you ask them to do more of the legwork to be "forgiven", or expect to work yourself on forgiving and forgetting?
What circumstances would cause you to lie to your partner?