What do you want from your relationship?
Do you really want your relationship to be based on money, power or something like that?
In some relations, maybe yes. We're all doing "fake it till you make it" but it's working with something you'll achieve sooner.
I'm a Python developer. I'm good at it. I'm applying a job which requires PHP skills. I say "Yes! I'm good at PHP!" but I'm not. What I'm good is Python. But both Python and PHP are scripting languages and I've the fundamental knowledge. Therefore, in a few months, I'll be at least over moderate with PHP too. I've just didn't studied until today. Now I need it, I'll learn.
Have you heard this song? "Ah yes!" (But I didn't, I'm going to listen it now.)
Do we really need this kind of things in our life? I mean come on, just tell you didn't listen that song but you will. You won't lose anything by being honest.
About the work example, I trust myself. I've fundamentals. I'll learn. What if I won't learn PHP? I'll get fired. No problem for the company.
These are just basic examples to show that lying eventually will cause problems.
What can you do right now?
Ask yourself. Why did you lied?
Possible reasons: He/she's so great, you feel like you don't deserve him/her. He/she's too good for you, smarter than you, has better looking than you etc.
Confess to yourself.
And then go tell him/her. "I've lied about this because I feel like (....) about my income, I feel like (....) about you and I feel like (.....) about myself.
Develop self-confidence. Build your relationships upon respect, love, honesty. Not little games, puzzles like they teach on TV.