| (a) October 15 and December 15 installment dates: | |
| (1) Tax without regard to Tax Reform Act of 1969 | $500 |
| (2) 80% of item (1) | 400 |
| (3) Minimum payment to avoid underpayment, determined without regard to Act: | |
| October 15, 1969 (25% of item (2)) | 100 |
| December 15, 1969 (25% of item (2)) | 100 |
| (4) Actual payment: | |
| October 15, 1969 | 90 |
| December 15, 1969 | 90 |
| (5) Amount of underpayment: | |
| October 15, 1969 ($100−$90) | 10 |
| December 15, 1969 ($100−$90) | 10 |
| (b) March 15 and July 15 installment dates: | |
| (1) Tax with regard to Act | 520 |
| (2) 80% of item (1) | 416 |
| (3) Less total of minimum payments to avoid underpayment, determined without regard to Act for October 15, 1969 and December 15, 1969 ($100 $100) | 200 |
| (4) Difference of items (2) and (3) | 216 |
| (5) Minimum payment to avoid underpayment, determined with regard to Act: | |
| March 15 (50% of $216) | 108 |
| July 15 (50% of $216) | 108 |
| (6) Actual payment: | |
| March 15 | 90 |
| July 15 | 90 |
| (7) Amount of underpayment: | |
| March 15 ($108−$90) | 18 |
| July 15 ($108−$90) | 18 |