Self-assessment - deduct costs

Hello everyone, unfortunately there were problems with our plumber. We set him several deadlines in writing due to various defects and incomplete work. Since he did not respond to this, we undertook the self-performance (as previously announced). Now it has come to pass that due to his lack of work we did not receive the BAFA funding and incurred other costs. We had to hire other craftsmen to complete the work. Now my question is: How will the costs be deducted from his invoice? We have the craftsmen's invoice including taxes, as well as net amounts such as the BAFA funding. He has also incorrectly invoiced some items in part.

Hi,

this is certainly difficult to assess within a forum.

What is the legal basis anyway? Can you enforce your claims with legal effect?
Are the incurred costs fully deductible or have additional costs arisen because you also made mistakes?

Technically, of course, you can strike out the incorrect items and justify it, add up the costs you incurred and finally deduct them from the remaining amount and transfer the new amount.
But be sure that you are right, you will probably receive letters from a lawyer.
At least I can take a look at how your chances look. If you have legal protection insurance, get legal counsel.

Best regards, Jann