Me and my spouse we both self-employed in a business. We both own the business and will file married jointly. I paid my estimated tax through IRS, how to pay my spouse's estimated tax? Do we both need to pay? How do we earn credits for social security. Thank you!
If you are self-employed you are required to pay self-employment tax for Social Security and Medicare---that is how you are building credits for Social Security.
https://ttlc.intuit.com/community/self-employed/help/what-is-the-self-employment-tax/00/25922
https://ttlc.intuit.com/questions/2902389-why-am-i-paying-self-employment-tax
Please explain "we both own the business." What is the business? How is it set up? Is it a sole proprietorship, an S-corps, C-corps or partnership?
Are you new to self-employment? You are posting from online Deluxe, which cannot provide a schedule C if you need to enter business expenses. Please provide more information.
The easiest way to pay your quarterly taxes to the IRS is at www.irs.gov/payments.
If you both own the business, then at a minimum I would expect you to be reporting business income/expenses on a 1065-multi-member LLC/Partnership tax return. But maybe you are in a community property state where you can actually split things down the middle and each report your half on a SCH C? Maybe it's set up as an S-Corp and you are both employees of that S-Corp? I don't know. I'm just guessing.