The IRS will always attempt to work out a payment plan. That does not necessarily mean they will wave interest and penalites. Been there. Done that.

>>Not attaching the check will cause her to pay significantly more. The IRS will add interest and penalties that could easily double or triple the owed amount.
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>Not necessarily.
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>Many years ago when I was a college student I wound up owing more in taxes than I had at tax time (over $1000 IIRC). I called the IRS before tax day - threw myself on their mercy, and was given 6 months to pay up - no penalty or interest.
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>At least it worked back then.
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>Of course, if I didn't pay in the 6 months I may have become a Kansas resident by way of Leavenworth.