since we don't know your income it's hard to say wether owing $900 is a lot
this is what the w-4 says for step 2
(b) Use the Multiple Jobs Worksheet on page 3 and enter the result in Step 4(c) below; or
(c) If there are only two jobs total, you may check this box. Do the same on Form W-4 for the other job. This
option is generally more accurate than (b) if pay at the lower paying job is more than half of the pay at the
higher paying job. Otherwise, (b) is more accurate .
none of these methods are truly accurate especially if pay varies from pay period to pay period or you get bonuses or other forms of additional compensation. also if you have non-wage income that can result in you owing.
