There is no federal credit for filing jointly. What you get is lower tax rates for you total income. Depending on how close your two income are to each other; i's possible that there is no savings by filing Married Filing Jointly vs. previously Filing Single or (less often) filing Married Filing Separately.
You can do comparisons with this tool: https://turbotax.intuit.com/tax-tools/calculators/taxcaster/?s=1
Also see: https://ttlc.intuit.com/questions/1894449-is-it-better-for-a-married-couple-to-file-jointly-or-separ...
