Can I reconstruct partnership books from bank data?

You can use bank data as part of a reconstruction, but do not pretend the reconstructed ledger was the contemporaneous record if it was not. The safe professional move is transparency.

A good reconstruction separates:

• customer receipts;
• transfers between accounts;
• partner contributions;
• loan proceeds;
• deductible expenses;
• owner distributions;
• asset purchases;
• debt principal payments; and
• unsupported or unresolved items.

Then tie the reconstruction to the filed Form 1065 and label assumptions. The audit risk is not that you used imperfect data. The risk is sending a polished ledger that hides gaps, estimates, or unsupported classifications.