Line 6 of form 2210
This number is usually line 25d of your current tax return.
The IRS instructions for form 2210 are on page 3:
Enter the taxes withheld shown on the following lines:
- Form 1040 or 1040-SR, line 25d;
- Form 1040-NR, lines 25d, 25e, 25f, and 25g;
- Also, Schedule 3 (Form 1040), line 11, if you filed the above forms;
- Form 1041, Schedule G, line 14. Filers of Form 8689,