Hello, thank you for your question. The amount taxed on social security depends on how much social security benefits received and total income from all sources. I am going to include a couple helpful links. The first is from the irs and how social security is taxed. The second is a TurboTax article that explains a little more detail. The third is refund estimator. This will help you see what your tax situation will look like based on estimates so you can pick the proper witholdings. I hope this helps and I answered your question.