The Ministry we tithed to in 2011 claims our donations are NOT tax deductable because the ministry does not have a 501c3 status. Is this true?

If the ministry meets the definition of a church, then it is not required to be approved by the IRS as a 501(c)(3) organization (by filing Form 1023).

From the IRS -
Some organizations are not required to file Form 1023. These include: Churches, interchurch organizations of local units of a church, conventions or associations of churches, or integrated auxiliaries of a church, such as a men's or women's organization, religious school, mission society, or youth group.

That being said it is possible the leaders know the organization does not meet the definition of a Church which is to lengthy for this discussion.

In addition, to claim the deduction you will need written documentation from the organization if your contributions exceed $250.

If the ministry meets the definition of a church, then it is not required to be approved by the IRS as a 501(c)(3) organization (by filing Form 1023).

From the IRS -
Some organizations are not required to file Form 1023. These include: Churches, interchurch organizations of local units of a church, conventions or associations of churches, or integrated auxiliaries of a church, such as a men's or women's organization, religious school, mission society, or youth group.

That being said it is possible the leaders know the organization does not meet the definition of a Church which is too lengthy for this discussion.

In addition, to claim the deduction you will need written documentation from the organization if your contributions exceed $250.

If your ministry told you that they do not meet the requirements, then you can not deduct the money.

They either have to be a church, which requires regular meetings ( don't have to be every week) They have to have a regular meeting place ( this can be a published home church address or a meeting room at a holiday inn or a actual separate meeting place) There is little requirements on doctrine, membership requirements and so on.

But if they are a church, and do not take in donations over a certain amount, they are allowed 501 3C status automatically without applying.

If they are a ministry, lets say a group that feeds the homeless, then they have to apply and get a letter from the IRS to be tax deductable.

So if your ministry told you they are not, they should know.