In this question, we need to arrange the sources of tax revenue for the Union Government in India in ascending order as per the Budget Estimates for 2013-14. The options given are as follows:

Option 1: 1-2-3-4

Option 2: 1-2-4-3

Option 3: 2-1-3-4

Option 4: 4-3-2-1

Based on the provided options, none of them seem to be correct because the correct answer is not given.

The correct order of the sources of tax revenue for the Union Government in ascending order for the Budget Estimates for 2013-14 is as follows:

1. Service tax

2. Union excise duties

3. Corporation tax

4. Customs

It is important to note that this order may vary in different years or based on changes in tax policies.